Diagnostic uncertainty in respiratory sarcopenia: accuracy of available tests and clinical implications: a systematic review and meta-analysis

PURPOSE: Respiratory sarcopenia (RS) is an emerging clinical condition associated with pneumonia and mortality, but its diagnosis remains uncertain because standardized criteria are lacking. This systematic review and meta-analysis evaluated the diagnostic accuracy of peak expiratory flow rate (PEFR), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) for identifying RS in older adults. METHODS: Eight databases were systematically searched for studies involving adults aged ≥60 years. Risk of bias was assessed using QUADAS-2. Test-specific and overall pooled sensitivity and specificity were calculated for PEFR, MIP, and MEP according to the operational definitions adopted by the primary studies. RESULTS: Seven studies comprising 2,466 participants were included (mean age range, 70.2-80.6 years). Overall pooled sensitivity was 0.614 (95% CI 0.453-0.753) and specificity was 0.726 (95% CI 0.443-0.898), with substantial heterogeneity (bivariate I²=0.929). Test-specific analyses showed distinct profiles: MEP-based approaches had relatively higher sensitivity and lower heterogeneity, MIP-based approaches had comparatively higher specificity, and PEFR-based approaches showed lower and more variable diagnostic performance. Meta-regression found no statistically detectable differences by sex or sarcopenia diagnostic criteria; however, these analyses were exploratory and underpowered. CONCLUSION: Respiratory muscle-related measures show variable diagnostic performance for identifying RS. Current evidence is insufficient to establish the superiority of any single test or recommend a clinical reference standard. Prospective multicenter studies using standardized criteria and diverse populations, together with international consensus on RS definition, are needed to support future clinical recommendations. REGISTRATION NUMBER: PROSPERO-CRD42023494910.