Evaluating the suitability of prediction equations for lung function in Indian children: a practical approach.
OBJECTIVE
Although several prediction equations to evaluate peak expiratory flow rate (PEFR) of Indian children are available in literature, clinicians and researchers need to make a logical choice of which equation to use as reference. The aim was to demonstrate a practical approach to making such a logical choice by using prediction equations on our study population.


METHODS
Eighteen linear regression equations generated on Indian children were chosen from available literature. PEFR measured on a Wright peak flow meter on 81 boys and 60 girls, aged between 8 and 13 years, was compared with the predicted values obtained from the equations. Data was systematically analyzed for the extent of over-estimation and under-estimation, correlation between the predicted and measured values and bias and limits of agreement using Bland-Altman plots.


RESULTS
The correlation between observed and predicted values using the eighteen equations ranged between 0.616 and 0.797 (for all P < 0.001). The Bland-Altman plots indicated that for all but three equations in boys and three equations in girls, lower measured values of PEFR were associated with higher predicted values. A final choice of a reference prediction equation was based on a combination of factors which included a high correlation between actual and predicted PEFR values, the bias of the estimate, the limits of agreement and the extent to which equations over or under-estimated PEFR.


CONCLUSIONS
A practical approach to evaluate the applicability of prediction equations on an independent data set has been demonstrated.
Swaminathan
Sumathi
S
Institute of Population Health and Clinical Research, St. Johns National Academy of Health Sciences, Bangalore, India.
Diffey
Bronwyn
B
Vaz
Mario
M
D000293:Adolescent; D000886:Anthropometry; D002648:Child; D005260:Female; D006801:Humans; D007194:India; D008297:Male; D010366:Peak Expiratory Flow Rate / Q000502:physiology*; D012016:Reference Values; D012129:Respiratory Function Tests / Q000592:standards*; D012574:Schools; D014109:Total Lung Capacity / Q000502:physiology*; D014797:Vital Capacity / Q000502:physiology