The accuracy of Influenza A (H1N1) “swine flu” laboratory testing: A systematic review of diagnostic test accuracy

Abstract

Background Influenza A (H1N1) recently became pandemic, highlighting the need for a cheap and accurate diagnostic test to diagnose this virus in a clinically relevant timeframe. The current reference standard (viral culture) requires a significant degree of technical expertise, laboratory time, resources and can take up to ten days to obtain a result, during which time there could be a significant spread of infection. Objectives To obtain summary estimates of the diagnostic accuracy of currently available laboratory tests compared to viral culture for the diagnosis of Influenza A (H1N1) from respiratory samples. Inclusion criteria Types of participants Patients presenting with influenza-like illnesses and who underwent both an index and reference test specific for influenza A (H1N1). Focus of the review The diagnostic test accuracy of tests for laboratory tests for Influenza A (H1N1) Types of studies Diagnostic test accuracy studies that compared the diagnostic accuracy of any laboratory test (index test) compared to viral culture as the reference test were considered for inclusion. Search strategy Diagnostic tests are still poorly indexed by major databases; therefore the search strategy was deliberately very broad and was conducted across 14 major databases during May 2010. Methodological quality Methodological quality was determined using the QUADAS checklist. Overall the methodological quality of the studies was moderate, however all suffered from incomplete reporting. Data collection Data was collected to determine the accuracy of the index tests and completeness of the conduct and reporting. Patients were identified as being either H1N1 positive or negative on the basis of the viral culture results. The index test results were then compared for sensitivity and specificity. Data synthesis Meta analysis was not appropriate as the included studies were heterogeneous, therefore data was synthesized in narrative summary. Results The search identified 3843 studies. Of these 56 full text articles were retrieved for further analysis. Twenty nine articles were critically appraised, with 24 being excluded on the basis of incongruence with the review objective or for containing insufficient detail. The remaining five cross sectional studies examined the diagnostic accuracy of polymerase chain reaction (PCR), and were included. Two studies reported accuracy measures and when reported, the sensitivity and specificity of PCR was high. Conclusions Although unable to generate a summary estimate of the overall accuracy of PCR, the available evidence suggests that PCR using respiratory specimens appears to be highly sensitive and specific at identifying patients with H1N1. Implications for practice When reported, PCR had high test sensitivity and specificity compared with viral culture, suggesting that patients were accurately being diagnosed by this method and in a much shorter timeframe. Caution should be taken interpreting these results, as this is based on the findings from two included studies Implications for research This systematic review highlights the need for better reporting and indexing of studies that examine the diagnostic accuracy of laboratory tests in general, and H1N1 specifically. This rapidly expanding area of research needs structure and consistency in order for its findings to be useful to health care clinicians and decision makers.