Importance of using lung function regression equations appropriate for ethnic origin

Abstract

Functional residual capacity (FRC) can be assessed reliably in young children using a helium gas dilution technique. The aim of the present study was to determine if differences in lung volume are found in asthmatic children of different ethnic origins. Eighty-eight children were studied, 53 of Caucasian origin and 35 of Afro-Caribbean origin. Their median age was 6.1 years (range, 5.3-9.0 years). FRC measured by helium gas dilution is reported as a percentage of predicted for height, using a published regression equation as well as regression equations appropriate for the ethnic origin of the child. In the majority of both groups FRC was elevated above the ethnically appropriate regression equation for healthy children. The Caucasian children apparently had higher FRCs than the Afro-Caribbean children if comparing the absolute lung volume, and if lung volume was expressed as percent of predicted for height, by a regression equation uncorrected for ethnic origin (P less than 0.02). This difference disappeared when ethnically appropriate regression equations were used. We conclude that lung volumes are similar in asthmatic children of different ethnic origin and that it is important to use ethnically appropriate regression equations.

Functional residual capacity in healthy preschool children

“…The present data are comparable to the predicted values in the second study by GREENOUGH and co-workers [9], in which the first regression equations were corrected for ethnic origin, and with those of the study by DOERSHUK et al [16] in children 1 month to 5 yrs of age using the plethysmographic method. Furthermore, our values are very close to the published tentative equation from STOCKS and QUANJER [10] based on individual data of three different laboratories: FRC He (mL) =0.0031 · H 2.56 · k, when k (representing a constant to indicate significant differences between laboratories) has a value of 1.4, as is the case in the second study of GREENOUGH and co-workers [9].…”

“…That no significant influence of gender has been observed by others in the same age group may be due to the smaller number of children studied [7][8][9]. As can be seen in table 3, the regression values in the present study are comparable to those in adults and children of 120 cm or more.…”

“…Furthermore, our values are very close to the published tentative equation from STOCKS and QUANJER [10] based on individual data of three different laboratories: FRC He (mL) =0.0031 · H 2.56 · k, when k (representing a constant to indicate significant differences between laboratories) has a value of 1.4, as is the case in the second study of GREENOUGH and co-workers [9].…”

“…The wide variation in normal values observed in the literature may, besides the technical difference in equipment, be explained by a different definition of normal controls: in some studies, controls are even included that have mild asthma [10,18]. Ethnic differences also play an important role [9,10]. A detailed description of the normal controls is therefore mandatory [10,12,15].…”

“…One of the techniques which can be applied in this age group is the determination of functional residual capacity (FRC), which requires only the passive co-operation of the child [7,8]. In previous studies of FRC in preschool children, it has already been demonstrated that FRC measurements can be performed in that age group [7][8][9]. There remains, however, much discrepancy between the few prediction equations available, and further modelling is needed to assess the potential influence of gender, weight, posture and age [10].…”