TITLE:    Reference lung function of Nigerian school-age children measured with electronic peak flow meter: comparison with local and Global-Lung-Initiative equations   

Abstract

Introduction. Spirometric reference equations (REs) assists diagnosing, monitoring and prognosticating respiratory diseases. However, spirometers are scarce in respiratory care in low-resource settings, hampering optimal care. Cheaper, simpler-to-use electronic peak-flow-meters (ePFM ) which measure both peak expiratory flow (PEF) and forced expiratory volume in one-second (FEV 1 ) may serve alternative utility. However, their use requires REsfitted to local populations. We compare ePFM-measured PEF and FEV 1 of Nigerian children with published local/foreign REs, including the Global-Lung-Function-Initiative (GLI) equations.Methods. PEF and FEV 1 of healthy pupils aged 6-11 years in Lagos-Nigeria was cross-sectionally measured with ePFM (Asma-1, Vitalograph, UK). PEF was compared to published local and foreign equations using Bland-and-Altman analysis. Goodness-of-fit of FEV 1 to GLI-equations was defined as mean (SD) predicted z-scores < 0.5 (1.0), 5% z-scores < -1.64 (% lower-limit-of-normal, LLN), 5% > 1.64 (% upper-limit-of-normal, ULN).Results. 766 children [mean (SD) age: 8.9 (1.6) years; 53.1% girls] achieved mean (SD) PEF and FEV 1 of 235.8 (52.0) L/min and 1.40 (0.34) L; higher in boys (p < 0.001), and strongly correlated with height (r=0.73-0.86), lower-limb-length (r=0.67-081), weight (r=0.62-0.76), age (r=0.60-0.66), upper-segmentvolume (r=0.58-0.69), upper-segment-length (r = 0.54-0.61) and chest-circumference (r=0.52-0.66). PEF agreed poorly with local and foreign equations, with wide limits-of-agreement.GLI-African-American equations fitted our FEV 1 [mean (SD; %LLN, %ULN)-girls: -0.17 (1.10; 9.1%, 5.4%), boys: 0.03 (1.11; 7.2%, 7.5%)]; GLI-global and GLI-othersdid not fit. Conclusion:Our FEV 1 fitted GLI-AA, albeit less so for girls. The most appropriate GLI FEV 1 equations for our population require bench-marking with clinical outcomes.