Molecular bacterial detection in nasopharyngeal swabs does not predict the clinical course of lower respiratory tract infections in primary care: an ancillary study of a randomized controlled trial
In brief
Primary care patients recovered in 7 days whether swabs found bacteria
In this analysis of 345 primary care patients with lower respiratory infections, 41% had bacteria detected in nasopharyngeal swabs, but median recovery time was 7 days in both groups. Bacterial detection also did not predict recovery time or symptom duration, regardless of antibiotic prescription, raising questions about the value of these tests for guiding care.
- Journal
- The British journal of general practice : the journal of the Royal College of General Practitioners (Q1)
- Published
- 2 November 2026
- Study design
- Randomized controlled trial
- Evidence level
- Level 1, High (CEBM 1b)
- Authors
- José Knüsli, Loïc Lhopitallier, Andreas Kronenberg, Marc-Antoine Perrenoud, Marie-Anne Page, Aline Mamin, et al.
- PMID
- 42971712
- DOI
- 10.3399/BJGP.2026.0056
Why clinicians should know about it
- Picked for Family Practice (paper of the day, 3 November 2026): Primary-care respiratory infection findings relevant to antibiotic stewardship
Abstract
BACKGROUND: Point-of-care molecular tests on easily collected samples could support antimicrobial stewardship in primary care. AIM: To determine whether molecular bacterial detection in nasopharyngeal swabs is associated with a worse disease course in patients with lower respiratory tract infections (LRTIs). DESIGN AND SETTING: Secondary analysis of a randomized controlled trial including 469 consecutive patients with LRTI, from 60 primary care practices in Switzerland. METHODS: Polymerase chain reaction assays for respiratory viruses and bacteria were retrospectively performed on nasopharyngeal swabs. Kaplan-Meier analyses and a multivariate Cox regression were used to evaluate time to recovery according to bacterial detection. RESULTS: A total of 345 patients were included, of which 142 (41%) had bacteria detected. The detection of bacteria did not influence median time to recovery (7 days in both groups, 95% confidence interval [CI] 6-8 days, p=0.29). Bacterial detection was not associated with time to recovery (adjusted hazard ratio 1.13, 95% CI 0.84-1.50, p=0.42), nor was the interaction term between bacterial detection and antibiotic prescription (adjusted hazard ratio 1.10, 95% CI 0.64-1.90, p=0.74), indicating independence from antibiotic treatment. The detection of bacteria was not associated with a different median duration of cough, sputum, or dyspnoea. The median duration of cough of any severity was 16 days (95% CI 15-18 days). CONCLUSION: Among patients with LRTI in primary care, molecular detection of bacteria in nasopharyngeal swabs did not predict a worse disease course. These findings cast doubts on the utility of syndromic molecular testing for managing LRTIs in this setting.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.