Assessing the quality of forced vital capacity measurement in patients with systemic sclerosis

Forced vital capacity (FVC) is an important tool for monitoring lung functions in patients with systemic sclerosis (SSc). However, several disease manifestations may influence the quality of FVC test in SSc. We aimed to assess the quality of FVC measurements according to current guidelines in patients with SSc and determine the factors that may affect results.

In this cross-sectional study, SSc patients and age/sex matched controls underwent spirometry. Quality of FVC measurements were graded according to updated American Thoracic Society (ATS) and European Respiratory Society (ERS) guidelines. Demographics, clinical features and parameters that may affect FVC test quality were compared between SSc patients with high and low quality FVC test.

98 SSc patients (90 female) and 100 controls were included. The rate of high quality FVC measurement in SSc patients was significantly lower in SSc patients compared to controls. (80 % vs 60.2 % p = 0.002). Among SSc patients; diffuse disease, ILD, anti-topoisomerase 1 antibody positivity, immunosuppressive use, flexion contractures of hands, reduced mouth opening and decreased chest expansion were more frequent in patients with low quality FVC (p < 0.05 for all). Patients with muscle weakness and medium/high risk of malnutrition were also numerically higher in low quality FVC group. Presence of more than one condition that may affect FVC quality was significantly higher among patients with low quality FVC.

A significant percent of SSc patients had low quality FVC measurement. Physicians should be aware of this point while interpreting FVC test results especially in SSc patients with more than one condition that may affect the quality of the test.