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Evaluation of a commercial Loop‐mediated Isothermal Amplification (LAMP) assay for rapid detection of Pneumocystis jirovecii
Author(s) -
Scharmann Ulrike,
Kirchhoff Lisa,
Schmidt Dirk,
Buer Jan,
Steinmann Joerg,
Rath PeterMichael
Publication year - 2020
Publication title -
mycoses
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.13
H-Index - 69
eISSN - 1439-0507
pISSN - 0933-7407
DOI - 10.1111/myc.13152
Subject(s) - loop mediated isothermal amplification , pneumocystis jirovecii , serial dilution , gold standard (test) , detection limit , positive predicative value , multiplex , biology , medicine , virology , predictive value , human immunodeficiency virus (hiv) , chromatography , pathology , chemistry , dna , bioinformatics , genetics , alternative medicine
Summary Background Various tools are obtainable for the detection of Pneumocystis jirovecii , among them qPCR promising highest sensitivity. A novel molecular method is commercially available, the loop‐mediated isothermal amplification (LAMP) assay. Objectives We compared the performance of the LAMP eazyplex ® Pneumocystis jirovecii with the RealStar Pneumocystis jirovecii PCR 1.0 qPCR. Material/Methods Overall, 162 lower respiratory tract specimens from 146 critically ill patients were investigated. LAMP assay and qPCR were carried out according to the manufacturer's recommendations. Positive results of the LAMP were described as time to positivity (TTP). The limit of detection (LOD) of the LAMP was analysed using 10‐fold serial dilutions of a high positive P jirovecii respiratory sample. For each serial dilution, TTP of the LAMP was plotted against cycle threshold (Ct) values of the qPCR. Results The LOD of the LAMP was determined to be approximately 4 × 10 3 copies/mL. While the LAMP revealed 28 (17%) positive signals from 20 patients, by using qPCR 41 (25%) positive samples from 28 patients were identified. Overall agreement with qPCR was 92%. Five false‐negative, one false‐positive and nine invalid results were detected by the LAMP. Positive and negative predictive values were 96% each, and sensitivity and specificity were 84% and 99%, respectively. There was a low correlation between the TTP and the fungal load. Conclusion The LAMP is a time‐saving and easy‐to‐perform method. It can be used as an alternative diagnostic method. However, for quantification purposes the qPCR is still the gold standard.