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2004 PT Survey Report - Findings
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Prothrombin Time Testing Practices in the Pacific Northwest:
A Model for Monitoring Voluntary Practice Guidelines
 
 
Survey Home
 
Findings
 
 
Purposes for performing PT testing
Participants were asked if they performed PT for any of the following purposes:
  • evaluation of bleeding,
  • detection of factor deficiencies,
  • assessment of liver disease,
  • monitoring of oral anticoagulation therapy, and
  • other.
Of the 297 respondents, 263 (89%) stated that they performed PT for at least one of the 4 indications, with one respondent performing PT (for evaluation of bleeding and detection of factor deficiencies) but not monitoring oral anticoagulation therapy. There were 5 respondents (2%) who did not note whether they performed PT assay for any of the 4 specific reasons above. Of the respondents, 28 (9%) noted that they did not perform PT for any of the above 4 indications and 1 (0.3%) stated not monitoring for oral anticoagulant therapy without answering if they performed PT for any of the other 3 specific indications.
 
Table 3 - Purposes for performing PT testing
Purpose Proportion* (Number)
Monitoring of oral anticoagulation therapy 99.6% (262)
Evaluation of bleeding 84% (205)
Assessment of liver disease 76% (177)
Detection of factor deficiencies 67% (153)
Other responses were pre-surgical testing, deep vein thrombosis, chest pain, baseline for cardiac profile, lupus anticoagulant testing, and whatever the doctor wanted.
*Proportions of affirmative responses after exclusion of those not responding affirmatively to at least one of the 4 specific indications noted for PT testing.
 
Since the focus of this questionnaire was the use of PT testing to monitor oral anticoagulation therapy, only participants responding affirmatively to such a use were asked to complete the remainder of the questionnaire.
 
Performing PT testing in more than one location
Given a list of choices, participants were asked if PT testing was performed in more than one location in their facility. Seventy-seven of 262 respondents (29%) answered "Yes" to this question.
 
Table 4 - Other Locations where PT testing is performed (N = 77*)
Location Number (Proportion*)
Anticoagulation clinic 39 (51%)
Patient draw station 18 (23%)
Patient exam room 13 (17%)
Nursing station 10 (13%)
Other responses (N = 28, 36%) were endoscopy department, patient bedside, chemotherapy room, home health, emergency department, satellite laboratory, core laboratory, outpatient clinic, hospital in another city, and home.
*The denominator used for proportions was the number of respondents (N = 77) checking at least 1 of the 4 choices. There was a respondent who had not checked any choices but had noted a testing site other than the central laboratory in the section labeled other. This respondent was included in the denominator.
 
Participants were asked to answer the remaining questions for the method they performed and not for testing done in any other location in their facility.
 
Patient self-testing devices
Of 259 respondents, 13 (5%) were aware of PT testing being performed by their patients on a self-testing device.
 
Thromboplastin reagents used
Two hundred and fifty-one respondents gave a manufacturer and/or brand name of the thromboplastin reagent used. One hundred seventy six (70%) indicated they used a reagent associated with a traditional PT test method and 75 (30%) noted the use of reagent test strips or cartridges associated with POC testing devices. Table 5 shows the demographics of sites according to these 2 different types of methods.
 
Table 5 - PT test methods (N = 251 sites)
Percent of Sites (N)
Hospital IL POL
Traditional methods 61 (108) 13 (22) 26 (46)
POC devices 6 (5) 1 (1) 92 (69)

 
Traditional methods
Sensitivity of PT assay to heparin. According to consensus guidelines developed at the 1997 CAP conference on laboratory monitoring of oral anticoagulation therapy, users should determine the sensitivity of their PT assay to heparin and, where possible, select a reagent that is insensitive to heparin in the therapeutic range (3). Therefore, participants were asked if they determined the sensitivity of their PT assay to heparin and if they selected a reagent that is insensitive to heparin in the heparin therapeutic range. In patients where rapid anticoagulation is required, heparin may be used initially and overlapped with warfarin for several days. Many thromboplastin reagent package inserts give an indication of the sensitivity of their reagent to heparin.
 
Of the respondents using traditional methods, 15% (26/169) determined the sensitivity of their assay to heparin and 54% (83/154) stated they selected a reagent that was insensitive to heparin in the therapeutic range. This is primarily an important feature for hospitalized patients and we found that 20% (22/112) of the hospital respondents determined the sensitivity, 58% (62/107) selected an insensitive reagent, and 64% (69/108) did one or the other to alleviate this concern about heparin interference with PT assays.
 
ISI values. When using the PT test to monitor oral anticoagulation therapy, the sensitivity of the thromboplastin reagent to the depletion of vitamin K dependent coagulation factors is reflected as the international sensitivity index (ISI). All thromboplastins are calibrated against standards with sensitivities comparable to the WHO international reference plasma, which is assigned an ISI of 1. Commercial manufacturers of thromboplastin reagents calculate the ISI and include it in the product package insert.
 
Several voluntary practice standards and other publications recommend the use of thromboplastin reagents that have a low ISI value (3-7). Thromboplastins with low ISIs are more responsive or "sensitive." The variability of INR values produced by different test systems may be reduced by the universal use of highly responsive reagents.
 
While sensitive thromboplastin reagents with lower ISI values may offer the potential for improved precision in determining the INR [due to the fact that INR = (PT ratio)ISI where PT ratio = patient PT/mean normal PT], some studies have suggested that low-ISI reagents may be less precise (6). The following recommendations have been made for the selection of reagent ISI values:
0.90-1.70   CAP (3)
<1.51   CLSI (4)
Close to 1.00   American Society of Health System Pharmacists (5)
<1.21   Hirsch (6)
<1.51   American Heart Association (7)

 
Table 6 shows the ISI ranges of the reagents used for PT assay.
 
Table 6 - PT reagents - Traditional methods (N = 176 sites)
Reagent manufacturer Number of respondents Examples of brand names Range of ISI values*
Dade Behring 58 Innovin
Thromborel S
0.90-1.13
Thromboplastin C+ 1.77-2.21
Beckman Coulter/ Instrumentation Laboratory 50 IL PT-Fibrinogen Recombinant
IL PT-Fibrinogen HS+
0.85-1.13
IL PT-Fibrinogen HS 1.35-1.44
IL PT-Fibrinogen
IL Thromboplastin
2.00-2.23
BioMerieux 24 HTF 1.15-1.26
Simplastin Excel 1.81-1.91
Diagnostica Stago 13 Neoplastin
Neoplastin C1+
1.26-1.35
Hemoliance 11 Recombiplastin RTF 0.94-1.03
Brain thromboplastin 2.00-2.33
Sigma Diagnostics/
Sigma Trinity Biotech
10 Thrombomax HS
Thromborel HS
1.15-1.31
Thrombomax 1.69-1.71
Pacific Hemostasis 6   1.16-2.04
Ortho 3 None given 0.85 to 1.00
Other 1 MLA Recombiplastin 1.03
Total 172   0.85-2.33
*There were 4 respondents who noted the name of their reagent manufacturer without providing their reagent's ISI.
 
For sites using traditional methods, the range of ISI values for their reagents was 0.85 to 2.33, with an average ISI of 1.34 and median ISI of 1.15 (N = 172). Table 7 shows a frequency distribution of the reagents used according to ISI values.
 
Table 7 - Distribution of reagents by ISI values (N = 172 sites)
ISI Values Number (Proportion)
< 1.20 91 (53%)
1.20-1.49 36 (21%)
1.50-1.69 3 (2%)
1.70-1.99 20 (12%)
2.00-2.40 22 (13 %)

 
When asked if they used a voluntary practice standard to guide them in the selection of their reagent, 25% (43/174) using traditional methods responded "Yes," and 21% (36/174) gave the name of a voluntary practice standard or guideline. The following summarizes these responses:
 
Voluntary practice standard Number of sites
CLSI 29
CAP 12
WHO   5
Chest   2
Archives of Pathology & Laboratory Medicine   2
American Society of Thrombosis & Hemostasis   1
 
Other sources mentioned  
Manufacturer's recommendations   4
Corporate standards   2
COLA   2
Code of Federal Regulations (CFR)   1

 
The majority of the respondents noted that they either did not use voluntary practice standards or were not aware of them. Of the respondents using traditional methods, 38% (66/174) responded "No" and 37% (65/174) responded "Do not know." The reasons given by sites that did not use a standard are summarized as follows:
 
Reason Number of sites*
Not aware of practice standards addressing this 32
Performed our own studies 20
Performed our own literature review 17
Recommended by manufacturer for our instrument   8
Cannot afford to purchase practice standards   7
Reagent selected to match/correlate with another lab   2
Reagent selected by corporate or parent lab   2
Do not agree with the standard   1
Reagent is common in our area   1
We are part of a buying group   1
*Based on the response patterns to this question, and others questioning why respondents did not use a voluntary practice standard, we chose to reflect only affirmative responses as numbers in rank order. Those responding that they were not aware of practice standards tended to not answer any subsequent questions. We considered 1 response pattern to be contradictory: not being aware of practice standards while not agreeing with the standard. In such a case, both affirmative responses were excluded. One respondent was excluded due to such an inconsistent response pattern.
 
Point of care devices
Of the respondents using POC devices, 3% (2/66) determined the sensitivity of their POC reagents to heparin and 14% (8/58) stated they selected a reagent that was insensitive to heparin in the therapeutic range. Of the 5 hospitals performing POC methods, none determined the sensitivity of the PT assay to heparin and only 1 s tated selecting a reagent that was insensitive to heparin in the heparin therapeutic range. The following table summarizes the POC devices used by the respondents:
 
Table 8 - PT reagents - POC devices (N = 75 sites)
Manufacturer Examples of Brand names Number of Respondents ISI values
Roche Diagnostics CoaguChek
CoaguChek S
61 2.00 (29 sites)
1.00 ( 2 sites)
No value given (30 sites)
International
Technidyne
Corporation
Hemochron Jr
Protime
Protime 3
8 1.00
Bayer Diagnostics PT-NC
RapidPoint
Thrombocard
5 1.00-1.20
Hemosense INRatio 1 1.00

 
When asked if they used a voluntary practice standard to guide in their selection of their PT reagent, 11% (7/65) of the respondents using POC devices said "Yes" and 11% (7/65) named a standard. The following summarizes their responses:
Voluntary practice standard Number of sites
CAP 2
CLSI 1
Other sources mentioned*
Manufacturer's recommendations 2
JAMA, American Journal of Clinical Pathology, and CAP 1
COLA 2
*There were 2 respondents noting CLIA as other sources even though CLIA is known to be regulatory and not a voluntary practice standard.
 
Of the respondents using POC devices, 45% (29/65) responded "No" and 45% (29/65) responded "Do not know." The reasons given by sites that did not use a standard are summarized as follows:
 
Reason Number of sites
Not aware of practice standards addressing this 17
Standards do not apply to my method   9
Performed our own literature review   3
Performed our own studies   3
Reagent is matched to our instrument   2
Test system is POC device, finger stick method   2
Cannot afford to purchase practice standards   1
ISI and calibrations set at factory, predetermined   1
Do not use reagent   1
Follow manufacturer guideline   1

 
Testing personnel
Given a list of personnel training backgrounds, participants were asked to list the numbers of each type of personnel that performed PT testing. A wide variety of backgrounds of testing personnel were given. Different patterns were seen in testing personnel between the sites using traditional test methods and those using POC devices.
 
Traditional methods
There was an average of 10 testing personnel per site, with a range of 1 to 70 per site (median, 6; N = 158). Ten different training/experience backgrounds were given. Of the 174 sites answering this question, 173 (99%) employed at least one medical technologist or medical laboratory technician as testing personnel.
 
Table 9 - Testing personnel performing traditional methods (N = 174 sites)
Testing personnel background Sites employing testing personnel with the background
  Number Percent
Medical technologist 171 98
Medical laboratory technician 99 57
On the job trained 9 5
Pharmacist 3 2
Registered nurse 3 2
Laboratory assistant 3 2
Phlebotomist 3 2
Non-registered tech 2 1
Medical assistant 2 1
Advanced registered nurse practitioner 1 0.6

 
Point of care devices
There was an average of 6 testing personnel per site, with a range of 1 to 100 per site (median, 4; N = 64). Twelve different training/experience backgrounds were given. Of the 74 sites answering this question, 46 (62%) employed at least one medical technologist or medical laboratory technician as testing personnel.
 
Table 10 - Testing personnel using POC devices (N = 84 sites)
Testing personnel background Sites employing testing personnel with the background
  Number Percent
Medical technologist 34 46
Medical assistant 33 45
Medical laboratory technician 27 36
Registered nurse 23 31
On the job trained 13 18
Licensed practical nurse 12 16
Pharmacist 4 5
Phlebotomist 4 5
Physician assistant 3 4
Laboratory assistant 2 3
Emergency medical technician 1 1
Advanced registered nurse practitioner 1 1

 
Specimen collection and handling
Participants were asked if they collected samples for PT by venipuncture. Of the 260 respondents to this question, 216 (83%) indicated they did.

Sodium citrate concentration. Several voluntary practice standards or guidelines recommend the use of collection tubes containing sodium citrate in the concentration of 3.2% (3, 8-10). The INR can be affected by the citrate concentration. Many of the manufacturers determine their ISI values using 3.2% citrate; therefore, the same citrate concentration should be used in individual laboratories. Low ISI reagents yield higher INR values when under-filled samples are collected in 3.8% citrate (11).

Of the 206 sites answering this question, 190 (92%) used only the recommended citrate concentration of 3.2% . The following table summarizes the responses.
 
Table 11 - Citrate concentration of specimen collection tubes (N = 206 sites)
Sodium citrate concentration Number of respondents Percent
3.2% 190 92
3.8% 8 4
3.2 % and 3.8% 2 1
Do not know concentration 1 0.5
Did not choose a concentration 5 2

 
When asked if they used a practice standard to guide their selection of citrate concentration of the collection tubes used, 39% (82/209) stated "Yes," and 34% (69/205) named a voluntary practice standard. The following summarizes their responses:
 
Voluntary practice standard Number of sites
CLSI 63
CAP 24
WHO   5
International Society of Thrombosis & Hemostasis (ISTH)   1
American Society for Clinical Pathology (ASCP)   1
Other sources mentioned
Manufacturer recommendations   5
Selected by corporation   2
Selected by local laboratory   1
*There was 1 respondent noting CLIA and Washington State regulations as other sources even though they are regulatory and not voluntary practice standards.
 
Sixty-four of the 209 respondents (31%) stated "No" and 63 (30%) responded "Do not know." The reasons given by sites not using a standard are summarized as follows:
Reason Number of sites*
Not aware of practice standard addressing this 32
Performed our own literature review 20
Performed our own studies 15
Cannot afford to purchase practice standards   6
Follow manufacturer's recommendations   6
To correlate with another laboratory   5
Standards do not apply to my method   3
Collection tubes already in place before I started   2
Corporate decision   2
A reference lab supplies us / Wish to standardize with reference lab   2
Advised by hospital   1

 
*We considered 1 response pattern to be contradictory: not being aware of practice standards while not agreeing with the standard. In such a case, both affirmative responses were excluded. One respondent was excluded due to such an inconsistent response pattern.
 
Specimen rejection criteria. Of the 216 respondents that collected samples by venipuncture, 202 (94%) said they had a written policy addressing specimen acceptability and rejection for PT testing.
 
There are many voluntary practice standards that address the proper collection of specimens for coagulation testing and PT testing in particular (4, 8, 12).
 
When asked if they used a practice standard to develop their specimen collection policies, 46% (94/205) of respondents said they did, and 37% (75/205) named a voluntary practice standard. The following summarizes their responses:
 
Voluntary practice standard Number of sites
CLSI 67
CAP 17
WHO   5
ASCP   2
ISTH   1
Other sources mentioned*
Manufacturer recommendations 16
Literature study, reference books   4
COLA   2
CLIA   2
Corporate decision   1
*There were 2 respondents noting CLIA as other sources even though CLIA is known to be regulatory and not a voluntary practice standard.
 
Fifty-two of 201 respondents (26%) responded "No" and 55 (27%) responded "Do not know." The reasons given by those who did not use a standard are summarized as follows:
Reason Number of Sites*
Not aware of practice standard addressing this 28
Performed our own studies 15
Performed our own literature review 13
Cannot afford to purchase practice standards   5
Standards do not apply to my method   3
Follow manufacturer's recommendations   3
Used a policy from where I worked before   1
*We considered 1 response pattern to be contradictory: not being aware of practice standards while not agreeing with the standard. In such a case, both affirmative responses were excluded. One respondent was excluded due to such an inconsistent response pattern.
 
Participants were given a list of issues that are commonly recommended for inclusion in specimen acceptability and rejection policies for coagulation testing. They were asked to acknowledge those they included in their written policy.
 
Table 12 - Specimen acceptance and rejection policies
Specimen acceptance/rejection issue Proportion (Number)*
Properly anticoagulated specimen 97% (194)
Correct volume of blood 97% (194)
Appropriate storage temperature 97% (189)
Time delays prior to testing 96% (187)
Adequate labeling of specimen 96% (190)
Adequate centrifugation (speed and time) 92% (178)
Information on requisition and specimen label match 90% (174)
Adequate information on requisition 90% (173)
Hemolysis 89% (170)
Appropriate transport times 89% (168)
Order of multiple tubes 86% (166)
Lipemia 78% (146)
Drawing specimens from patient lines 73% (136)
Icterus 71% (131)
Difficult draws 67% (127)
Collection of samples in a syringe 66% (129)
Abnormal hematocrits 65% (123)
Heparinized specimens 60% (113)
* Number refers to those responding affirmatively to each question and proportions are the percent affirmative responses of all responding either affirmatively or negatively to each question. There was 1 respondent noting that they had a written specimen acceptance/rejection policy for presence of lupus anticoagulant.
 
It should be noted that depending on the setting or the methodology, some of specimen rejection criteria may not apply. For example, the collection of samples from patient lines and heparinized specimens may be applicable for patients in hospitals, but not for most patients in outpatient settings. Specimens that are icteric or lipemic may affect test methods based on optical clot detection, but may not be a concern for mechanical clot detection methodologies.
 
Of the 259 respondents, 85 (33%) stated that they collected samples by finger stick or capillary collection. Of the 82 respondents, all collecting capillary samples, 71 (87%) indicated that they had a written policy addressing the proper collection of capillary specimens for PT testing.
 
Checking out new lots of reagents
Various practice standards address issues associated with implementing new lots of testing reagents. Some address general activities such as establishing or verifying patient reference ranges and mean of normal, and some are specific for handling new lots of thromboplastin reagents (3-5, 12, 13).
 
Given a list of 8 indicators of quality practices associated with checking out new lots of thromboplastin reagents for PT testing, participants were asked which ones they performed.
 
Traditional methods
 
Table 13 - Checking out new lots of reagents - Traditional methods
Quality Practice Proportion (Number) *
Establish patient mean of normal 95%(158)
Conduct parallel testing between lots 93% (156)
Verify reference (normal) range 92% (153)
Confirm calculations of INR 89% (148)
Verify that the ISI is correct for instrument/reagent combination 89% (147)
Alert clinicians when new reagent or reagent with different ISI placed in use 66% (107)
Perform correlation studies with another method or site 42% (67)
Establish ISI with calibrators 20% (32)
*Number refers to those responding affirmatively to each question and proportions are the percent affirmative responses of all responding either affirmatively or negatively to each question.
 
When asked if they used a practice standard to develop their policy for checking out new lots of reagents, 37% (63/172) said they did, and 32% (55/172) named a voluntary practice standard. The following summarizes their responses:
 
Voluntary practice standard Number of sites
CLSI 44
CAP 23
WHO   1
ASCP   1
ISTH   1
Other sources mentioned* Number of sites
Manufacturer recommendations 10
Performed our own studies   2
Follow corporate policy   1
*There were 2 respondents noting CLIA as other sources even though CLIA is known to be regulatory and not a voluntary practice standard.
 
Fifty-nine of the 172 sites (34%) responded "No" and 50 (29%) responded "Do not know." The reasons given by those not using a standard are summarized as follows:
 
Reason Number of sites*
Not aware of practice standard addressing this 36
Performed our own studies 21
Performed our own literature review 12
Cannot afford to purchase practice standards   5
Follow manufacturer's recommendations   4
Follow CAP policy, CAP website   2
To correlate with hospital   1
*We considered 1 response pattern to be contradictory: not being aware of practice standards while not agreeing with the standard. In such a case, both affirmative responses were excluded. One respondent was excluded due to such an inconsistent response pattern.
 
Point of care devices
 
Table 14 lists selected practices followed by the respondents.
 
Table 14 - Checking out new lots of reagents - POC devices
Quality practice Proportion (Number)*
Verify reference (normal) range 62% (36)
Verify that the ISI is correct for instrument/reagent combination 60% (35)
Perform correlation studies with another method or site 40% (22)
Establish patient mean of normal 35% (19)
Conduct parallel testing between lots 35% (19)
Confirm calculations of INR 34% (19)
Alert clinicians when new reagent or reagent with different ISI placed in use 33% (19)
Establish ISI with calibrators 30% (17)
*Number refers to those responding affirmatively to each question and proportions are the percent affirmative responses of all responding either affirmatively or negatively to each question.
 
When asked if they used a practice standard to develop their policy for checking out new lots of reagents, 25% (16/65) of the respondents said they did, and 5% (3/65) named a standard. The following summarizes their responses:
Voluntary practice standard Number of sites
CLSI 2
CAP 1
Other sources mentioned Number of sites
Follow manufacturer recommendations 8
Test controls 3
COLA 1
Recommended by company 1

Thirty of the 65 sites (46%) responded "No" and 19 (29%) responded "Do not know." The reasons given by those not using a practice standard are summarized as follows:

 
Reason Number of sites
Not aware of practice standard addressing this 17
Standards do not apply to my method   9
Performed our own literature review   4
Follow manufacturer's recommendations   4
Performed our own studies   3
Standards are too complicated   1
Method is waived; calibrated at the factory   1
Not aware needed for POC device   1
Use pre-packaged reagents   1
Cannot afford to purchase practice standards   1

 
Patient test reports
The WHO, along with the ISTH, recommends that reporting of PT results for patients on oral anticoagulation therapy include the use of INR values (10, 14). Other practice standards and publications suggest this as well (3, 4, 6, 12). Given a list of choices, participants were asked which test values and other information they provide in the patient report to clinicians.

Table 15 lists the measurement units and results interpretations/comments provided by the respondents.
 
Table 15 - Patient test reports
Test value Proportion (Number)*
PT as INR 99.6% (232)
PT in seconds 89% (204)
PT ratio 7% (14)
Other responses were patient mean of normal value (N = 4), normal control value (N = 2), QC (N = 1), therapeutic ranges (N = 1), and last dose of medication (N = 1). In all these cases, PT was reported in both seconds and INR.
Interpretation or comments
Reference (normal) ranges 84% (211)
Specimen comments 79% (195)
Therapeutic ranges 74% (182)
Interpretation 30% (66)
Other responses were dose of medication (N = 5), clinician seeing patients and knowing what ranges/interpretations are (N = 2), extenuating circumstances (N = 1), and normal patient mean (N = 1).
*Number refers to those responding affirmatively to each question and proportions are the percent affirmative responses of all responding either affirmatively or negatively to each question.
 
Repeating patient tests
To evaluate how personnel judge test result acceptability, we asked what prompted them to repeat a patient test result, given a list of choices.
 
Table 16 - Reasons for repeating a patient test
Reason Proportion (Number)*
Instrument failure or flag 99% (255)
Quality control values outside of acceptable limits 97% (243)
Critical patient value 95% (244)
Unusual value for patient's history 82% (204)
Abnormal patient value 59% (148)
Information from patient interview 34% (80)
Computer tracking system 29% (69)
Other responses were perform tests in duplicate (N = 2), if clinician requests it (N = 2), doctor tracking results on patient chart (N = 1), invalid test result (N = 1), and delta check (N = 1).
*Number refers to those responding affirmatively to each question and proportions are the percent affirmative responses of all responding either affirmatively or negatively to each question.
 
General quality assurance (QA) and competency assessment activities
Given a list of 10 QA procedures, participants were asked which they performed. The responses are summarized in the following table.
 
Table 17 - Quality assurance procedures
Quality assurance procedure Proportion (Number)*
Immediately alert clinician about critical test results 100% (254)
Verify performance of new analytical test systems 95% (225)
Participate in proficiency testing for PT testing 91% (232)
Assure that clinician receives patient test results 91% (229)
Periodically verify calibration of all instrumentation 86% (212)
Compare instrument printout to reported patient value 78% (183)
Compare patient value to previous values (delta check) 73% (178)
Monitor rate of critical values reported 45% (109)
Monitor rate of patient specimen redraws 38% (93)
Monitor rate of patient test repeats 32% (77)
*Number refers to those responding affirmatively to each question and proportions are the percent affirmative responses of all responding either affirmatively or negatively to each question.
 
Given a list of 6 approaches to evaluate the competency of testing personnel, participants were asked to indicate which they used. The following table summarizes their responses.
 
Table 18 - Competency assessment
Competency assessment activity Proportion (Number)*
Successful performance of QC 97% (246)
Review of procedure manuals 89% (226)
Direct observation of testing 87% (219)
Participation in continuing education 80% (201)
Analysis of unknown samples 77% (193)
Periodic written examination 26% (64)
*Number refers to those responding affirmatively to each question and proportions are the percent affirmative responses of all responding either affirmatively or negatively to each question.
 
Onsite Visits
As part of this study, we also performed focused on-site reviews of PT testing in 25 sites in the State of Washington. Any site that performed PT testing, with a routine MTS survey due between November 2003 and June 2004, was included in our sample. In addition, 1 review was performed during a validation survey of a hospital accredited by the Joint Commission for Accreditation of Healthcare Organizations and 1 as part of a complaint investigation. Fifteen different instrument/reagent combinations (including traditional methods and POC devices) were represented in this sample. During these onsite visits we observed actual testing practices, reviewed written policies, worksheets, patient test reports, manufacturer's product inserts and manuals, and interviewed staff on problems and concerns related to their PT testing. Thirteen of the 25 sites visited also completed the mailed questionnaire, and we were able to validate their responses on the survey questions in that they agreed using the 2 data collection approaches.
 
Discussion
 
One of the primary goals of this study was to determine if laboratory testing personnel use voluntary practice standards to develop their policies and practices. We focused on 4 areas important for PT testing:
  • anticoagulant concentration in the specimen collection tube,
  • specimen acceptance and rejection policy,
  • selection of reagent with low ISI, and
  • verification of the reference range and mean of normal of the reagents.
Of those responding, a minority (22-46%) stated using voluntary practice standards. The most commonly mentioned standards were those developed by the CLSI and CAP. Respondents relied on a variety of other resources for establishing their policies and practices. Manufacturers recommendations, journal articles, Government regulations, accreditation standards and corporate policies were commonly noted. The most common reason given for not using practice standards was lack of awareness (51-60%). Testing sites also said they performed their own studies (24-31%) and searched the literature (19-32%). Sites using POC devices commonly said that practice standards were not applicable for their testing, because the tests were CLIA-waived, they used finger stick specimens only, or that certain variables were pre-set by the manufacturer. Very few respondents said they could not afford (8-10%) or did not agree (0-1%) with practice standards.

Of the respondents performing venipuncture collections, 94% had a written specimen acceptance/rejection policy. The vast majority of respondents (92%) exclusively used the recommended sodium citrate concentration of 3.2%. For sites using traditional testing methods, the majority (76%) used a reagent with an ISI of <1.70, verified their reference range (92%), and established their mean of normal (95%) for new lots of thromboplastin reagents.

For sites using POC devices, specimens are primarily obtained by finger stick or capillary collection methods. The issues of collection tubes and transport, processing, and storage of samples are not applicable in those cases. Respondents using POC devices relied more on information provided by the manufacturer for reference ranges and mean of normal values. The CLSI has a proposed standard that addresses point-of-care monitoring of anticoagulation therapy that can be a good resource for these testing sites (15).

By sharing this report with study participants, we hope to raise awareness of practice guidelines and other references that may help to harmonize practices among all sites performing PT testing. An awareness of laboratory practice standards must also be raised by professional societies, including those representing physicians, nurses, medical assistants, and others who commonly perform laboratory testing as a component of their overall health care activities. Sites using POC devices may benefit from the development of new practice standards that are written with POC devices, settings and personnel in mind. In addition, there needs to be an acknowledgement of a balance between practice standards and other legitimate resources for the development of harmonized practices between laboratories, such as manufacturer information, Government regulations and accreditation organization standards.

Another primary goal of this study was to evaluate quality indicators in both general laboratory practices and for PT testing specifically. By raising awareness about common and best practices, it is hoped that testing personnel may investigate and adopt new practices based on a comparison to their peers.

Throughout this report we acknowledge differences between POC and traditional methods that have an effect on laboratory practice variables. When testing occurs at point of care, the testing personnel have access to more patient information than is typically available in a traditional hospital or an independent laboratory setting. A review of the medical record and/or interview with the patient may allow for the immediate assessment of test result acceptability and timely resolution by specimen recollection, test repeat or referral. The collection of capillary specimens alleviates several issues related to transport, processing, storage and time delays that must be addressed by the traditional laboratory setting. Manufacturers of POC devices research practice guidelines as evidenced by their references to them in their product inserts. For POC devices, the manufacturer addresses many QC and QA activities: pre-set calibration and calculations, electronic controls, instrument flagging, and established reference ranges. As a result, this allows for less reliance on practice standards to develop policies and procedures, fewer QC and QA activities by the user, and less rigorous programs for training and competency assessment than for traditional testing methods.

Because clinicians compare patient INR values against standardized therapeutic ranges and monitor trends in an individual patient's INR values over time, consistency in test values from an individual laboratory and agreement in values from different laboratories are issues of key importance. One very vulnerable step in PT testing occurs when laboratories introduce new lots of reagents. The laboratory may not recognize that the reagent sensitivity has changed and may not perform studies to identify that the patient's INR values may have shifted. Verification of the ISI value in the product insert with every lot of reagents (whether a change is expected or not) is a simple, but effective, solution to help alleviate serious calculation errors (16). Laboratories should establish their own patient mean of normal when using new reagents, and they should perform parallel testing between old and new lots. Laboratories must assure that ISI and mean of normal values are correctly entered into their instrument and laboratory information systems when calculating INRs, and they must alert clinicians when there is a change in INR values that may affect their ability to judge patients' coagulation status.

Consistency of test results between laboratories can be improved when sites use reagents with low ISI values, when they use collection tubes with 3.2% sodium citrate, and when they report PT results as INRs. Although not always feasible and not required by CLIA, every site regardless of their setting or methodology, should know how their INR values compare with those in another site. It is common for near-patient settings to refer samples with questionable critical values to another site for confirmation. Clinicians need to know where test results are coming from and how results from different laboratories compare.

In this study, we found that nearly a third (29%) of our respondents knew of PT testing performed in another location in their facility. We also found that only 42% of laboratories performing traditional methods and 40% of those using POC devices performed a correlation with another method or site. By knowing the bias between methods, testing personnel can judge the acceptability of their own method and assist clinicians in judging the clinical significance of differences in values obtained on an individual patient tested at the 2 sites. In addition, both sites should communicate with each other and with clinicians, whenever new methods or reagents are introduced that may change the established bias. Another correlation study may be warranted in these instances. In one published study, authors found that statistically INRs are clinically equivalent if they are within 0.4 of a target value of 2.5 and within 0.7 of a target value of 3.5 (17).

In a 2001 study commissioned by the Agency for Healthcare Research and Quality to identify practices likely to improve patient safety, patient self-management of warfarin therapy was identified as an intervention with strong evidence supporting wide-spread implementation (18). In our study, we found this practice to be uncommon (5% of respondents).
 
Authors' contributions: Both authors had access to all study data. Ms LaBeau takes responsibility for the integrity of the data, and Dr Shahangian accepts responsibility for the accuracy of data analyses.

Study concept and design: LaBeau, Shahangian

Acquisition of data: LaBeau

Analysis and interpretation of data: Shahangian, LaBeau

Drafting of the manuscript: LaBeau

Critical revision of the manuscript for important intellectual content: Shahangian, LaBeau

Administrative, technical, or material support: LaBeau, Shahangian

Study supervision: LaBeau, Shahangian
 
References
 
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10. International Committee for Standardization in Haematology/International Committee for Thrombosis and Haemostasis recommendations for reporting prothrombin time in oral anticoagulation control. Thromb Haemost 1985;53:155-156.

11. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol 1998;109:754-757. [Abstract]

12. The Ontario Association of Medical Laboratories, Quality Assurance and Clinical Laboratory Practice Committee. CLP 014 Guidelines for the Laboratory Monitoring of Oral Anticoagulants.1997.

13. Clinical Laboratory Standards Institute. How to Define and Determine Reference Intervals in the Clinical Laboratory; Approved Guideline-Second Edition. Document C28-A2. 2000.

14. World Health Organization Expert Committee on Biological Standardization. 28th Report: WHO Technical Report Series 610, WHO, Geneva, pp 14-15 and 45-51; 1977.

15. Clinical Laboratory Standards Institute. Point-of-Care Monitoring of Anticoagulation Therapy; Approved Guideline. Document H49-A. 2004.

16. Centers for Disease Control and Prevention. Public health dispatch: Adverse events and deaths associated with laboratory errors at a hospital - Pennsylvania, 2001. MMWR 2001;50:710-711. [Full-Text HTML | PDF]

17. Lassen JF, Brandslund I, Antonsen S. International normalized ratio for prothrombin times in patients taking oral anticoagulants: critical difference and probability of significant change in consecutive measurements. Clin Chem 1995;41:444-447. [Abstract | PDF]

18. Shojania KG, Duncan BW, McDonald KM, Wachter RM, eds. Making Health Care Safer: A Critical Analysis of Patient Safety Practices. AHRQ Publication No. 01-E058. Rockville, MD: Agency for Healthcare Research and Quality. July 2001.


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