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Pneumocystis jirovecii pneumonia PCR test on upper respiratory tract swab
V Sivaraj1, P Cliff1, S Douthwaite1
1Guy's and St Thomas' NHS Foundation Trust, London, UK.
Objectives:
Pneumocystis jirovecii pneumonia (PCP) is an opportunistic fungal infection with high morbidity and mortality among people living with HIV. Upper respiratory tract (URT) swabs are routinely taken for testing viral and bacterial pathogens when patients present with respiratory symptoms in our hospital. We conducted a pilot service improvement project to explore the utility of URT swabs for PCP diagnosis using in-house real-time polymerase chain reaction (PCR).
Methods:
Ten URT swab samples obtained from HIV-positive patients with PCP and a positive PCP PCR (AusDiagnostics) from lower respiratory tract (LRT) samples were retrospectively identified. Nine HIV-positive patients with a negative PCR for PCP from LRT samples were identified. Stored aliquots of DNA extracted from these samples were retrieved and tested by an in-house real-time PCR for the presence of PCP DNA. Among PCP-positive cases, URT swabs collected after PCP treatment initiation were excluded from the study.
Results:
In all, 10 URT samples from PCP-positive patients and nine URT samples from PCP-negative patients were tested for PCP by real-time PCR. Eighteen out of 19 URT sample had a concordant result with the LRT samples. The sensitivity and specificity for URT sample PCR were 90% [confidence interval (CI): 55.50-99.75%] and 100% (CI: 66.37-100%). The positive predictive value was 100% and the negative predictive value was 90.9% (CI: 60.90-98.47%).
Conclusions:
Upper respiratory tract swab can reliably detect PCP DNA on real-time PCR among people living with HIV with PCP.
Insights
Upper respiratory tract swabs can reliably detect Pneumocystis jirovecii pneumonia (PCP) DNA in people with HIV using real-time PCR. This pilot study shows high sensitivity and specificity, suggesting URT swabs are a valuable tool for PCP diagnosis.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Molecular Diagnostics
Background:
- Pneumocystis jirovecii pneumonia (PCP) is a severe opportunistic infection in people with HIV.
- Respiratory symptoms in HIV patients often prompt testing for various pathogens.
- Current diagnostic methods for PCP may involve invasive procedures.
Purpose of the Study:
- To evaluate the utility of upper respiratory tract (URT) swabs for diagnosing PCP.
- To assess the performance of an in-house real-time polymerase chain reaction (PCR) assay for PCP detection in URT samples.
Main Methods:
- Retrospective analysis of URT swab samples from HIV-positive patients with confirmed PCP (positive lower respiratory tract PCR) and controls (negative LRT PCR).
- Testing of stored DNA extracts from URT samples using an in-house real-time PCR assay.
- Exclusion of URT samples collected after PCP treatment initiation.
Main Results:
- Eighteen out of 19 URT samples showed results concordant with lower respiratory tract samples.
- The in-house real-time PCR assay demonstrated a sensitivity of 90% and specificity of 100% for URT swabs.
- Positive and negative predictive values were 100% and 90.9%, respectively.
Conclusions:
- Upper respiratory tract swabs are a reliable method for detecting Pneumocystis jirovecii DNA via real-time PCR.
- This approach offers a potentially less invasive and effective diagnostic strategy for PCP in HIV-positive individuals.
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