Evaluation of lateral flow Immunoassay for the diagnosis of Cryptoccocal Meningitis

Abstract

Background. Cryptococcal meningitis is the most common opportunistic infection and the second leading cause of death in HIV infected persons in Africa. Many fatalities from cryptococcal meningitis can be averted by early diagnosis and treatment. The aim of this study was to evaluate and compare Lateral Flow ImmunoAssay (LFA) to latex agglutination (LA), India ink microscopy and culture using various sample types. Methods. A hospital based cross-sectional study was conducted at Mbagathi hospital, Nairobi, Kenya, from April to July 2017. The participants were enrolled through systematic random sampling. HIV patients suspected of cryptococcal meningitis who were scheduled for lumber puncture and routine blood sample collection were enrolled into the study prospectively. Capillary blood, serum and cerebral spinal fluid (CSF) samples were collected from the participants. LFA (IMMY, Norman, Ok) test was performed on capillary blood, serum and CSF and the test results compared with LA (IMMY, Norman, Ok) test performed on serum and CSF, india ink microscopy and culture on CSF. Sensitivity, specificity and predictive values were calculated and test agreement levels estimated using kappa (k) coefficients. Results. Of the 124 capillary blood and serum, and 99 CSF samples, the agreement between LFA and LA on serum was 94.4% and kappa of 0.88 with sensitivity and specificity of 100% and 91%. LA on CSF was 97.9% and kappa of 0.96 with sensitivity and specificity of 100% and 96%. The agreement between LFA and india ink (microscopy) was 96.9% and kappa of 0.94 with sensitivity and specificity of 100% and 94.1%. On CSF culture, the agreement was 72.7% and kappa of 0.43 with sensitivity and specificity of 100% and 64%. The agreement level of LFA on capillary blood, serum and CSF was 100% and kappa of 1.00 with sensitivity and specificity of 100% Conclusion. The high agreement between LFA, LA and india ink on different sample type shows that LFA is a reliable diagnostic test. The evidence of test agreement between LFA in capillary blood, serum and CSF coupled with the fact that it is easy and rapid to perform with accurate results forms the basis for LFA as a choice for point of care (POC) test for Cryptococcal meningitis.