Normative reference values for lung transfer factor in Isfahan, Iran

Objectives and background: Transfer factor or carbon monoxide diffusing capacity (DLCO) is a particularly valuable test of the appropriateness of gas exchange across the alveolocapillary membrane. The purpose of this study is to derive predictive equations for DLCO and its derivative volume-corrected DLCO (DLCO/VA) measured by single-breath method in a large non-smoking population sample in Isfahan. Methodology: We evaluated 1429 randomly selected subjects (732 men, aged 5-85 years). Gender-specific linear prediction equations were developed by multiple regression analysis; with measured DLCO, and DLCO/VA values (mmol/min/kPa), as dependent variables regressed against age (A), height (H) and body surface area (BSA). Results: For both genders, age had negative effects on DLCO, while height had a positive effect on DLCO and DLCO/VA (P < 0.01). The prediction equations for DLCO and DLCO/VA are: '0.152 x height - 0.056 x age - 11.595' and '-0.12 x age + 2.467', for men and: '-0.035 x age - 0.133 x height - 10.707' and '-0.012 x age - 0.02 x height + 2.755', for women, respectively. Conclusions: Our results therefore provide an original frame of reference for either DLCO or DLCO/VA in Iranian population, obtained from a standardized single-breath technique.