Positivity of polymerase chain reaction and Grocott staining in relation to the duration from therapy initiation to examination in Pneumocystis jirovecii pneumonia

Abstract

Introduction

The diagnosis of pneumocystis pneumonia (PCP) relies on microscopy and/or polymerase chain reaction (PCR) of bronchoalveolar lavage fluid (BALF). Although Pneumocystis jirovecii can be identified even after therapy initiation, the exact timeframe for reliable testing remains unclear. We investigated the relationship between diagnostic examinations for PCP and the duration from therapy initiation to the time of testing.

Materials and methods

We retrospectively collected data from 105 patients diagnosed with PCP based on the diagnostic criteria across four institutions from January 2019 to August 2024. The duration from therapy initiation to the time of testing and the corresponding test results were reviewed.

Results

Among 105 patients, 46 and 44 patients underwent P. jirovecii PCR and Grocott staining of BALF, respectively. Fifty-six patients underwent sputum examination. The positivity of P. jirovecii PCR in BALF appeared to decrease after therapy initiation in non–human immunodeficiency virus (HIV) patients. The positivity rate of Grocott staining was low regardless of treatment. All HIV patients had positive P. jirovecii PCR or Grocott staining results in BALF. Among patients with P. jirovecii PCR–positive results in BALF, the duration from therapy initiation to testing was significantly longer in HIV patients than in non–HIV patients (2.5 days [range 0–7] vs. 0 days [0–4], p < 0.001).

Conclusion

For non-HIV patients who have already received anti–PCP therapy, the use of BALF for PCP diagnosis should be performed as early as possible. In contrast, HIV-positive patients can still be diagnosed with PCP after therapy initiation.