Evaluation of rapid diagnostic methods for the diagnosis of cryptococcal meningitis in HIV positive patients in a health facility, Nairobi-Kenya.
East African Journal of Pathology. 2:18-22. Abstract
Background: Cryptococcal meningitis is a fatal opportunistic infection in immune-compromised patients. Lack of simple, affordable, rapid and specific methods for diagnosis in many government health facilities in Kenya has aggravated patients’ conditions.
Objective: This study was aimed at determining the performance of India ink (Microscopy), latex agglutination test (LAT) and enzyme immunoassay (EIA) in the diagnosis of cryptococcal meningitis in a Kenyan population.
Design: Laboratory based cross-sectional study.
Setting: A high-volume government health facility based in Nairobi.
Subjects: One hundred and thirteen CSF samples from HIV positive patients with signs and symptoms of cryptococcal meningitis sent to the laboratory for routine analysis.
Methodology: The study was approved by the KEMRI Scientific Committee/Ethics Review Committee and informed consent sought from the patients. The test for the agreement between the test methods and the gold standard (Culture) was calculated using the non-parametric McNemar’s test using SPSS version 17 (SPSS Inc., Chicago, IL) at 5% significant level.
Results: Twenty one point six percent of all samples tested positive on LAT while 9% were positive on microscopy, EIA and culture. The sensitivity, specificity, positive and negative predictive values for microscopy and EIA were: 90%, 99%, 90% and 99% respectively. By LAT, the values were: 100%, 86.1%, 41.7% and 100% respectively. Both EIA and microscopy had an agreement of 89% whereas that of LAT was 52.8% with the gold standard (C.S.F culture).
Conclusion: From the results of this study, it is evident that Latex Agglutination Test was the most sensitive among the study methods. Therefore, LAT is an appropriate diagnostic test but requires confirmatory testing. EIA could be an appropriate confirmatory test but is limited because it is not available in our setup. India ink though available is user-dependent, a major limitation. The use of test combinations did not increase the sensitivity of neither India ink nor enzyme immunoassay and is therefore not significant in the diagnostic work up for cryptococcal meningitis.
Recommendations: Local settings may consider frequent and unlimited use of LAT as a sensitive diagnostic tool for cryptococcal meningitis. It is also important to note that positive LAT tests are accompanied with a confirmatory test due to unfavourable specificities as evidenced from the research findings. In areas where cost is not a limitation, EIA may be used as a confirmatory test. Future research of comparing lateral flow immunoassay (LFA) and the current test methods using CSF in our hospital set up is warranted.