Evaluation of Lateral Flow Assay for the Diagnosis of Cryptococcal Meningitis and its Comparison with the Gold Standard and Other Laboratory Tests

Introduction: Cryptococcosis is a potentially fatal fungal disease affecting both immunocompromised and immunocompetent individuals. Hence, a Point Of Care Test (POCT) is required with higher sensitivity and specificity (100%), for the rapid detection of cryptococcosis which will be life saving for the patient.

Aim: To evaluate the usefulness of Lateral Flow Assay (LFA) for rapid detection of Cryptococcal Antigen (CrAg) from Cerebrospinal Fluid (CSF) sample.

Materials and Methods: This diagnostic/pilot study was conducted in Mycology Laboratory, Sri Ramachandra Medical College and Research Institute, Chennai, Tamil Nadu, India, over a period of six months (June 2019-November 2019). The CSF samples (n=37) from patients with suspected meningitis were considered for the study. Direct microscopy with gram stain, negative stain and histopathological stains was performed for all the CSF samples. Culture was done on basal medium, enriched media and special media. Cryptococcus genus specific Polymerase Chain Reaction (PCR) was also performed to confirm the isolates grown on the culture. Serological tests like Latex Agglutination Test (LAT) and LFA were also performed on all the samples. The LFA results were compared with microscopy, culture and LAT.

Results: Among the 37 suspected meningitis patients, three grew Cryptococcus in culture which was considered as the gold standard in the diagnosis of Cryptococcal Meningitis (CM). Direct microscopic techniques had 100% specificity however their sensitivity was less i.e., 67%. LAT had a sensitivity of 100% and specificity of 94%. However, LFA in present study had a very good sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) (100%).

Conclusion: The LFA for the detection of CM is considered to be an effective method when compared to the other conventional and serological methods with higher sensitivity and specificity. Hence, in present study authors evaluated the use of LFA in diagnosis of CM and found that this assay when used as a POCT, can give the results in short duration. Considering this as a pilot study, further studies including higher number of samples are essential to confirm the effectiveness of the findings.