Diagnostic performance of an in-house real-time polymerase chain reaction (PCR) assay and antigen detection from respiratory samples for the diagnosis of pulmonary cryptococcosis

Abstract

Introduction

The currently available diagnostic tests lack sensitivity to diagnose pulmonary cryptococcosis. In the current study, we developed and standardized an in-house real-time PCR assay and evaluated the antigen detection in respiratory samples for the diagnosis of pulmonary cryptococcosis.

Materials and Methods

We standardized an in-house real-time PCR assay (using URA5 and STR1 primers; index test 1) and cryptococcal antigen detection (BIOSYNEX® CryptoPS, France) from the respiratory samples (index test 2). We considered a sample positive for PCR assay when both gene targets (URA5 and STR1) were detected. We prospectively enrolled subjects undergoing evaluation for non-resolving pneumonia and evaluated the performance of the index tests for diagnosing pulmonary cryptococcosis. The reference standard was proven or probable pulmonary cryptococcosis diagnosed by EORTC/MSG (European Organization for Research and Treatment of Cancer/ Mycoses Study Group) criteria.

Results

Of the 133 subjects enrolled in the study, two (2.66 %) and three (3.99 %) were diagnosed as having proven and probable pulmonary cryptococcosis. 3.8 % of study subjects had HIV. The sensitivity and specificity of qPCR (index test 1) for the diagnosis of pulmonary cryptococcosis were 60.0 % (95 % CI: 14.6-94.7) and 96.1 % (95 % CI: 91.1-98.7), respectively, while the sensitivity and specificity of antigen detection from respiratory samples (index test 2) were 40.0 % (95 % CI: 5.2-85.3) and 99.2 % (95 % CI: 95.7 -100.0), respectively.

Discussion

In-house PCR and antigen detection in respiratory specimens can potentially be used for early diagnosis of pulmonary cryptococcosis. Larger multicenter studies are required to confirm their utility.