Abstract
Background Cryptococcus neoformans causes life-threatening meningitis. A recently introduced lateral flow immunoassay (LFA) to detect cryptococcal antigen (CRAG) is reportedly more rapid and convenient than standard latex agglutination (LA), but has not yet been evaluated in a diagnostic laboratory setting.MethodsOne hundred and six serum, 42 cerebrospinal fluid (CSF), and 20 urine samples from 92 patients with known or suspected cryptococcosis were tested by LA and LFA, and titres were compared. Results were correlated with laboratory-confirmed cryptococcosis. Serial samples were tested in nine treated patients.ResultsTwenty-five of 92 patients had confirmed cryptococcosis; all sera (n = 56) from these patients were positive by LFA (sensitivity 100%, 95% confidence interval (CI) 93.6–100%) compared with 51/56 positive by LA (sensitivity 91.1%, 95% CI 80.7–96.1%). Fifty sera from 67 patients without cryptococcosis tested negative in both assays. While LA yielded more false negative results (5/56) this did not reach statistical significance (p = 0.063). Nine CSF samples from patients with cryptococcal meningitis yielded positive results using both assays while 17/18 urine samples from patients with cryptococcosis were positive by the LFA. The LFA detected CRAG in C. gattii infection (n = 4 patients). Agreement between titres obtained by both methods (n = 38 samples) was imperfect; correlation between log-transformed titres (r) was 0.84. Turn-around-time was 20 minutes for the LFA and 2 h for LA. The cost per qualitative sample was 18USD and 91 USD, respectively and per quantitative sample was 38USD and 144USD, respectively.ConclusionsQualitative agreement between the LFA and LA assays performed on serum and CSF was good but agreement between titres was imperfect. Ease of performance of the LFA and the capacity for testing urine suggest it has a role in the routine laboratory as a rapid diagnostic test or point-of-care test.
Highlights
Cryptococcosis is a life-threatening infection caused by two main species, Cryptococcus neoformans and Cryptococcus gattii
Cryptococcus gattii, which is endemic in Australia, causes disease predominantly in immunocompetent hosts (87% of cases) [4,5,6] C. gattii has been reported as an emerging pathogen in British Columbia, Canada and in the United States [7,8]
We investigated the performance of the lateral flow immunoassay (LFA) for routine testing of samples within a hospital mycology laboratory using serum, cerebrospinal fluid (CSF) and opportunistic urine samples from the same patients
Summary
Cryptococcosis is a life-threatening infection caused by two main species, Cryptococcus neoformans and Cryptococcus gattii. Most cases of cryptococcosis are caused by C. neoformans (serotypes A, D and AD), predominantly in immunocompromised persons. In Australia, the incidence of infection in healthy hosts is high (31% of cases; overall incidence of 6.6 cases per million population/year) [4]. Cryptococcus gattii (serotypes B and C), which is endemic in Australia, causes disease predominantly in immunocompetent hosts (87% of cases) [4,5,6] C. gattii has been reported as an emerging pathogen in British Columbia, Canada and in the United States [7,8]. Meningitis is the commonest form of disease primary respiratory illness is more common in Southeast Asia [1]. A recently introduced lateral flow immunoassay (LFA) to detect cryptococcal antigen (CRAG) is reportedly more rapid and convenient than standard latex agglutination (LA), but has not yet been evaluated in a diagnostic laboratory setting
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