Predicted Reference Equations for Spirometry Indices as a Proxy from Anthropometry Measurements of Nigerian Children with Sickle Cell Anaemia Aged 5-12 Years

Background: Significant morbidity and mortality in patients with sickle cell disease are accounted for by lung complications. To facilitate good respiratory care for children with sickle cell anaemia the generation of local predicted values is highly important.

Objective: To determine the reference equations for spirometry indices estimation in children with sickle cell anaemia, which can be readily used as proxy when there is no easy accessibility to spirometer.

Methods: A cross-sectional study with linear regression models developed to estimate reference values for spirometric indices in Nigerian children with sickle cell anaemia aged 5-12 years.

Results: Age as independent variables for estimation of forced expiratory volume in 1 s (FEV1) was associated with lowest coefficient of determination (R2) and highest standard error. The coefficient of determination (R2) and standard error was highest and lowest, respectively, when arm span was used to determine peak expiratory flow rate (PEFR). Prediction models for PEFR and FEV1 gave the closest mean estimates that were 0.18 and 0.16 lower and higher than the actual mean PEFR and FEV1, respectively, but the differences was significant only in FEV1. On the contrary the prediction models for forced vital capacity (FVC) gave mean estimates that was 1.02 higher than the actual mean FVC, however, the finding was not significant.

Conclusion: Preferred proxy for spirometry indices in children with sickle cell anaemia may be arm span.