Evaluation of a point-of-care immunoassay test kit ‘StrongStep’ for cryptococcal antigen detection

Edward Mpoza, Liliane Mukaremera, Didas Atwebembere Kundura, Andrew Akampurira, Tonny Luggya, Kiiza Kandole Tadeo, Katelyn A. Pastick, Sarah C. Bridge, Lillian Tugume, Reuben Kiggundu, Abdu K. Musubire, Darlisha A. Williams, Conrad Muzoora, Elizabeth Nalintya, Radha Rajasingham, Joshua Rhein, David R. Boulware, David B. Meya, Mahsa Abassi

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21 Scopus citations


Background HIV-associated cryptococcal meningitis is the leading cause of adult meningitis in Sub-Saharan Africa, accounting for 15%–20% of AIDS-attributable mortality. The development of point-of-care assays has greatly improved the screening and diagnosis of cryptococcal disease. We evaluated a point-of-care immunoassay, StrongStep (Liming Bio, Nanjing, Jiangsu, China) lateral flow assay (LFA), for cryptococcal antigen (CrAg) detection in cerebrospinal fluid (CSF) and plasma. Methods We retrospectively tested 143 CSF and 77 plasma samples collected from HIV-seropositive individuals with suspected meningitis from 2012–2016 in Uganda. We prospectively tested 90 plasma samples collected from HIV-seropositive individuals with CD4 cell count <100 cells/μL from 2016–2017 as part of a cryptococcal antigenemia screening program. The StrongStep CrAg was tested against a composite reference standard of positive Immy CrAg LFA (Immy, Norman, OK, USA) or CSF culture with statistical comparison by McNemar’s test. Results StrongStep CrAg had a 98% (54/55) sensitivity and 90% (101/112) specificity in plasma (P = 0.009, versus reference standard). In CSF, the StrongStep CrAg had 100% (101/101) sensitivity and 98% (41/42) specificity (P = 0.99). Adjusting for the cryptococcal antigenemia prevalence of 9% in Uganda and average cryptococcal meningitis prevalence of 37% in Sub-Saharan Africa, the positive predictive value of the StrongStep CrAg was 50% in plasma and 96% in CSF. Conclusions We found the StrongStep CrAg LFA to be a sensitive assay, which unfortunately lacked specificity in plasma. In lower prevalence settings, a majority of positive results from blood would be expected to be false positives.

Original languageEnglish (US)
Article numbere0190652
JournalPloS one
Issue number1
StatePublished - Jan 2018

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Publisher Copyright:
© 2018 Mpoza et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


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