Race accounted for approximately 5% to 10% of variance in pulmonary diffusing capacity for nitric oxide (DLNO) when other factors such as age, sex, and height were controlled, according to study results recently published in BMC Pulmonary Medicine.

Results from a full battery of pulmonary function tests (PFTs) were compared between groups of patients of differing races, with the groups matched for sex, age, and height. Results for Black individuals were compared with a matched reference sample of White individuals. Multiple linear regression equations were developed.

Among the 59 healthy Black individuals in the study, 27 were men and 32 were women. When results from PFTs performed in Black individuals were compared with those of the matched sample of White individuals, the models demonstrated that sex, age, race, and height together explained 71% of the variance in diffusing capacity for carbon monoxide (DLCO) and DLNO. Race accounted for approximately 5% to 10% of the total variance.

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After adjusting for sex, age, and height, DLCO and DLNO in Black participants were 3.9 mL/min/mm Hg and 12.4 mL/min/mm Hg lower, respectively, than in the White reference sample — a difference researchers attributed to the lower alveolar volume found in Black participants.

The study authors wrote, “The results of this pilot data reveal small but important and statistically significant differences in DLNO and DLCO in adults. Future reference equations should account for racial differences.” Using reference equations designed for a White population could falsely diagnose lung disease in Black individuals, the investigators cautioned.


Zavorsky GS, Almamary AS, Alqahtani MK, Shan SHS, Gardenhire DS. The need for race-specific reference equations for pulmonary diffusing capacity for nitric oxide. BMC Pulm Med. Published online July 13,2021. doi:10.1186/s12890-021-01591-7