North-African reference values of alveolar membrane diffusion capacity and pulmonary capillary blood volume

In North-African adults, location-specific reference values for membrane diffusion capacity (D(m)) and pulmonary capillary blood volume (V(c)) were needed.

To verify the applicability of previously published reference equations for D(m) and V(c) in North-African healthy adults (age >18 years) and to determine specific reference equations for North Africa.

The study was designed as a prospective cross-sectional study. Anthropometric data (age, height, weight and body mass index) and D(m) and V(c) were assessed in 85 healthy Tunisian adults. Univariate and multiple linear regression analyses were used to determine reference equations and to calculate the lower limit of the normal range (LLN).

The mean ages ± SD (minimum - maximum) for male and female adults were 53 ± 21 (21-85) and 42 ± 16 (18-72) years, respectively. Previously published reference equations did not reliably predict measured D(m) and V(c). The reference equation (r(2) = 47%) for D(m) was -36.16 + 45.37 × height - 0.34 × age + 0.39 × weight + 7.41 × gender (0 = female and 1 = male). To calculate the D(m) LLN subtract 24.36 from the reference value. The reference equation (r(2) = 30%) for female V(c) was 94.70 - 0.57 × age, and the reference equation (r(2) = 52%) for male V(c) was 0.82 - 0.48 × age + 52.47 × height + 0.16 × weight. To calculate the V(c) LLN subtract 28.52 and 26.54 from these reference values for females and males, respectively.

These V(c) and D(m) reference equations supplement the international World Bank of reference equations.