The need for race-specific reference equations for pulmonary diffusing capacity for nitric oxide

Gerald Stanley Zavorsky,Shi Huh Samuel Shan,Douglas Shawn Gardenhire,Ahmad Saleh Almamary,Mobarak Khalid Alqahtani

doi:10.1186/s12890-021-01591-7

Abstract

BackgroundFew reference equations exist for healthy adults of various races for pulmonary diffusing capacity for nitric oxide (DLNO). The purpose of this study was to collect pilot data to demonstrate that race-specific reference equations are needed for DLNO.MethodsAfrican Americans (blacks) were chosen as the comparative racial group. In 2016, a total of 59 healthy black subjects (27 males and 32 females) were recruited to perform a full battery of pulmonary function tests. In the development of DLNO reference equations, a white reference sample (randomly drawn from a population) matched to the black sample for sex, age, and height was used. Multiple linear regression equations for DLNO, alveolar volume (VA), and pulmonary diffusing capacity for carbon monoxide (DLCO) using a 5–6 s breath-hold were developed.ResultsOur models demonstrated that sex, age2, race, and height explained 71% of the variance in DLNO and DLCO, with race accounting for approximately 5–10% of the total variance. After normalizing for sex, age2, and height, blacks had a 12.4 and 3.9 mL/min/mmHg lower DLNO and DLCO, respectively, compared to whites. The lower diffusing capacity values in blacks are due, in part, to their 0.6 L lower VA (controlling for sex and height).ConclusionThe results of this pilot data reveal small but important and statistically significant racial differences in DLNO and DLCO in adults. Future reference equations should account for racial differences. If these differences are not accounted for, then the risk of falsely diagnosing lung disease increase in blacks when using reference equations for whites.

Highlights

Pulmonary function tests (PFTs) are essential tools for modern clinical respiratory function assessment
The main barrier for nitric oxide (NO) uptake resides between the alveolar and red blood cell membranes (~ 60%) [28]. This advantage gives DLNO a better representation of gas transfer through the alveolar-capillary membrane compared to DLCO
DLNO is more affected by lung volume compared to DLCO, which makes the KNO a better measure than KCO in those with restrictive lung disease [33]

Summary

Introduction

Pulmonary function tests (PFTs) are essential tools for modern clinical respiratory function assessment They are used in the evaluation of patients with respiratory symptoms and for guiding the management of diagnosed lung disease. The main barrier for NO uptake resides between the alveolar and red blood cell membranes (~ 60%) (i.e. membrane resistance) [28] This advantage gives DLNO a better representation of gas transfer through the alveolar-capillary membrane compared to DLCO. The sensitivity in detecting cardiopulmonary disease may be improved using DLNO compared to DLCO [26] These examples demonstrate there is evidence that a DLNO test can be technically and physiologically superior to a DLCO test [26].

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