Commercial loop-mediated isothermal amplification (LAMP) assay for rapid diagnosis of Pneumocystis pneumonia: An alternative to immunofluorescence assays

A commercial loop-mediated isothermal amplification (LAMP) assay is available for the detection of Pneumocytis jirovecii (Eazyplex®, Amplex diagnostics, Germany). Few centers currently use this LAMP assay in France. Recently, the commercialization of reagents used to perform the P. jirovecii immunofluorescence assay (IFA) was stopped. This study aimed to assess the position of the commercial LAMP P. jirovecii assay in the diagnostic strategy for Pneumocystis pneumonia.

Over 24 months (August 1, 2021, to September 1, 2023), all bronchoalveolar lavage fluid (BALF) samples with a request for P. jirovecii detection were analyzed with the commercial Eazyplex® LAMP assay, using a Genie 2® device (Amplex, diagnostics), in parallel with the techniques used for direct examination. Specific P. jirovecii quantitative real-time PCR (qPCR) was subsequently performed.

In total, 346 BALF samples were analyzed by Diff-Quik coloration, IFA, and the commercial Eazyplex® LAMP assay for initial screening.

Twenty-six cases of PCP were retained based on radiological, biological and clinical criteria.

Among the 26 cases of PCP, 11 BALF samples were positive using the initial screening techniques: four with the three techniques, six by IFA and Eazyplex®, and one only by IFA. The eleven BALF samples were positive with the specific P. jirovecii qPCR assay, with a mean quantification cycle (Cq) of 27 [19–32].

The commercial Eazyplex® LAMP assay is able to provide a result in 25 min and its sensitivity is similar to that of BALF direct examination techniques, such as IFA, which is a technique no longer available on the European market. The sensitivity of the commercial Eazyplex® LAMP assay is however clearly inferior to that of the specific P. jirovecii qPCR assay and, therefore, cannot replace the specific qPCR, but may have a place in the diagnostic strategy.