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Results of the Survey of Hospital Coagulation Laboratory Practices, United States-2001
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Shahram Shahangian, Ph.D.; Ana K. Stanković, M.D., Ph.D.; Ira M. Lubin, Ph.D.;James H. Handsfield, M.P.H.; Mark D. White, B.S.
 

Also available in a print-friendly PDF version

 
bullet Executive Summary
bullet Introduction
bullet Methods
bullet Results and Discussion
bullet Concluding Remarks
bullet References
bullet Appendix
 

METHODS

Study Sample

The target population was U.S. hospital laboratories. The sampling frame was hospitals from the 1999 directory of the American Hospital Association (AHA). This database is not limited to the AHA members and includes 95% of all U.S. hospitals (personal communication, AHA, November 1999 and as verified against the Online Survey, Certification and Reporting database of CLIA-registered hospitals). This database includes the number of beds, permitting us to stratify hospitals by this variable as a surrogate measure of hospital size. We stratified hospitals into those with > 200 beds (large hospitals) and those with <200 beds (small hospitals). The randomly selected large and small hospitals in the study sample constituted 26% and 9% of the large and small hospitals listed in the sampling frame, respectively.

Questionnaire Development

We developed this survey questionnaire based on the recommendations of an advisory panel and numerous discussions and deliberations within the CDC. We began the process to develop the survey by formulating an initial set of questions that reflected these deliberations. The initial version of the questionnaire then underwent numerous revisions to improve clarity, brevity and formatting. We also asked a survey expert at the CDCs National Center for Health Statistics to review the clarity, framing and formatting of the survey questions. After revising the survey based on the comments we received, we pretested the questionnaire by sending it to laboratory management personnel of 9 hospital coagulation laboratories. (See the Appendix for a copy of the actual survey used.)

Following the recommendation of the U.S. Office of Management and Budget (OMB), we developed an Internet based questionnaire and offered it to all the respondents as an alternative means of responding to the survey. This electronic version mirrored the printed questions, answer selections and formatting. Additionally, it incorporated logical constraints to prevent the respondents from entering conflicting or contradictory answers.

Sample Size and Number of Beds

The rationale for sample size was based on the criterion of ensuring a maximum confidence interval of 6% for any estimated proportion within the selection strata. We used a random sample stratified by large hospitals (with > 200 beds) and small hospitals (with <200 beds) to ensure sufficient numbers of the respondents for the 2 strata so that we could analyze data separately for each. The purpose of examining large and small hospitals as separate groups was to determine whether they had different practice profiles regarding coagulation testing:

Type of facility

Population size (1999 AHA directory)

Size of selected sample (percent)

Small Hospitals (< 200 beds)

4,245

375 (9%)

Large Hospitals (> 200 beds)

1,662

425 (26%)

Total

5,907

800 (14%)

Below is the distribution of the number of beds for the final 632 respondents that composed 79% of the study sample.

 

Distribution of Number of Beds

Number of beds

Number of hospitals

Proportion of total

<50

101

16%

5099

98

16%

100149

71

11%

150199

41

6%

200249

86

14%

250299

64

10%

300349

45

7%

350399

34

5%

400499

27

4%

500599

25

4%

600799

23

4%

800999

11

2%

10001399

6

1%

01399

632

100%

Survey Implementation

Upon receiving the OMB approval for the survey, the CDC directed ASI to take the following steps:

  • identify and contact each laboratory director while verifying the hospitals mailing address,
  • print the survey questionnaires and post it on a secure CDC website,
  • mail the survey packets to the entire sample, providing each laboratory the option of responding electronically,
  • mail reminder postcards to each (potential) participant 1 week after mailing the printed survey, and
  • contact the non-respondents by telephone and, if needed, send additional survey packets.

Before selecting the study sample, we excluded laboratory personnel who were involved in pretesting the questionnaire. We also removed the institutions of members of the expert panel from the sampling frame.

We sent each questionnaire along with a cover letter addressed to the laboratory director by name. This letter included the identification code and the password for each hospital to enable them to respond electronically if they elected to do so. We administered this survey and collected results between June 2001 and October 2001. One week after the initial mailing of the questionnaire, ASI sent a reminder postcard to each respondent, and telephoned the non-respondents within 2 weeks after mailing the postcard. The purpose of the call was to confirm that the respondent received the survey, to encourage the hospital laboratory to participate, and to secure a commitment from the laboratory director to complete and return the survey. We followed up with non-respondents between July 2001 and September 2001. We were not able to contact 7 non-respondents.

Data Entry and Management

Two different individuals keyed the data from each paper survey. Data management personnel had the 2 separate data entries compared, identified any discrepancies, and documented these. A data entry supervisor then performed the adjudication process. The second quality assurance (QA) system used to assess the integrity of the data entry process consisted of examining 10% of the survey booklets after the rekey and adjudication of discrepancies. The auditor compared the survey booklet answers to the database to determine if the answers were correct.

Data Exclusion

We combined the databases containing responses from the 2 modes of data collection (paper and electronic) to create the final analysis database. We found 10 instances when the participant had responded both affirmatively and negatively to a question. We excluded these responses. There were also 9 other instances when the respondent had checked more than 1 selection, despite the instructions specifying that the respondent could check only 1 selection. We excluded all such responses. We also excluded all responses to a gate question and those relating to it if the survey instruction had specified that those subsequent questions not be answered. Due to such a problematic response pattern, we excluded all responses to 1 of the surveys 43 questions (Question 31) and the 3 subsequent sub-questions involving a total of 1,300 responses. We also excluded a total of 568 other responses because, after responding negatively to a gate question, participants provided answers to 1 or more subsequent questions.

After excluding the question and sub-questions noted above, there remained 153 questions and sub-questions involving 96,696 possible responses. The following illustrates how participants responded:

Response Pattern

Type of response

Number of responses

Proportion of total responses

Valid

62,321

64%

Blank

33,788

35%

Invalidresponse pattern

568

0.6%

Invalidly responding both yes and no

10

0.01%

Invalid response to more than 1 selection

9

0.01%

All

96,696

100%

Data Presentation and Statistics

Reported frequencies relate to affirmative responses we observed for yes-or-no questions and all responses checked in multiple-response questions. These frequencies did not include the excluded data noted above. Percent response in yes-or-no questions is percent of affirmative responses. Percent response in multiple-choice questions is percent of all those responding to 1 or more selection(s). For the check-all-that-apply type questions, these percentages may total > 100% if 1 or more respondents checked more than 1 selection. For the choose-only-one type questions, these percentages total 100% because we excluded all multiple responses from further analysis. We compared responses from large and small hospital laboratories using 2-tailed χ2 test. When significant (P < 0.050) differences existed, we provided response frequencies and percentages for large and small hospitals separately. We compared the number of professional certifications of the large and small hospital respondents by using 2-tailed t-test.
 


This page last reviewed: 7/12/2004
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