Pulmonary dysfunction among adolescents and adults with sickle cell disease in Nigeria: Implications for monitoring

Sir,

I refer to the interesting case–control study by Ozoh et al.[1] published in the October–December 2019 issue of the Annals of Thoracic Medicine. The authors nicely studied the frequency and pattern of spirometric abnormalities in a cohort of Nigerian adults with sickle cell anemia (SCA). They found that the median forced expiratory volume 1 (FEV1), forced vital capacity (FVC), and the FEV1/FVC were significantly lower in SCD as compared to controls (P = 0.000 in all instances). The frequency of abnormal pulmonary patterns was higher in SCD as compared to controls with abnormal spirometric pattern in 71% and 31.5% of participants with SCD and controls, respectively (P = 0.000). The restrictive pattern was predominant (48% vs. 23%), but obstructive (11.8% vs. 7.4%) and mixed patterns (11% vs. 0.9%) were also found among SCD versus controls.[1] The authors addressed few study limitations. I presume that the following methodological limitation could shadow more suspicions on the study results. The authors stated in the methodology that they referred to the Global Lung Function Initiative (GLI) reference equations[2] for the characterization of spirometric pattern. It is explicit that using population-specific spirometric standard could describe better the pulmonary function status than using a foreign population standard. Actually, GLI reference is old dated back to 2012 and it was constructed based on over 160,000 data points from 72 centers in 33 countries in collaboration with the European Respiratory Society global Lung function initiative.[2] It is not worthy to be specifically employed for Nigerian adult population. This is centered on the notion that applying prediction formula derived for other populations always overestimated the values for the African ethnic population.[3] Importantly, spirometric standards for healthy Nigerian adults have been already formulated to be employed in the clinical fields and researches institutions.[4] I wonder why Ozoh et al.[1] did not refer to that national standard in the study methodology. I suppose that if they employed that standard, more accurate results might be yielded. Despite the study limitations, the reported high burden of pulmonary dysfunction in the studied SCA cohort (71%)[1] is worrying. It requires regular monitoring of lung function to maintain pulmonary health status on one hand and improve the quality of life on the other.

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