NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.
CSTE Position Statement(s)
Invasive pneumococcal disease (IPD) is a notable cause of morbidity and mortality in the US, despite the availability of 7-valent pneumococcal conjugate vaccine (PCV7) and 13-valent pneumococcal conjugate vaccine (PCV13). After introduction of PCV7 in 2000, rates were reduced by 64-77% among adults and older children, and down to less than one case per 100,000 among children under 5 for the included serotypes. In 2010, PCV13 further lowered rates. However, in 2011 there were still more than 35,000 cases and 4,200 deaths from IPD, indicating a need for continued surveillance.
The ability to test for Streptococcus pneumoniae using culture independent diagnostic tests (CIDTs) like polymerase chain reaction (PCR)-based testing has become both more available and more common. PCR can be and is used for typing of Streptococcus pneumoniae, a key component of surveillance, and integrating CIDT identification into the case definition would increase overall coherence. Similar to the convention with other diseases, it is therefore suggested that a category of “probable” IPD cases be created, to classify CIDT positive but culture negative (or with absent culture results) individuals.
Invasive Pneumococcal (Streptococcus pneumoniae) Disease or IPD causes many clinical syndromes, depending on the site of infection (e.g., bacteremia, meningitis.)
Laboratory Criteria for Diagnosis
Supportive: Identification of S. pneumoniae from a normally sterile body site by a CIDT without isolation of the bacteria.
Confirmatory: Isolation of S. pneumoniae from a normally sterile body site.
Criteria to Distinguish a New Case from an Existing Case
A single case should be defined as a health event with a specimen collection date that occurs more than 30 days from the last known specimen with a positive lab finding.
A case that meets the supportive laboratory evidence.
A case that meets the confirmatory laboratory evidence.
The use of CIDTs as stand-alone tests for the direct detection of S. pneumoniae from clinical specimens is increasing. Data regarding their performance indicate variability in the sensitivity, specificity, and positive predictive value of these assays depending on the manufacturer and validations methods used. It is therefore useful to collect information on the laboratory conducting the testing, and the type and manufacturer of the CIDT used to diagnose each IPD case. Culture confirmation of CIDT-positive specimens is still the ideal method of confirming a case of IPD.