Accuracy of height and weight data from child health records
- 1Department of Social Medicine, University of Bristol, Bristol, UK
- 2Medical Research Council Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, UK
Background
Height and weight measurements routinely collected for child health records are potentially useful for both clinical practice and research, but there is limited knowledge of their accuracy.
Data and Methods
Height/length and weight measurements from clinics of the Avon Longitudinal Study of Parents and Children (ALSPAC) were used as a gold standard against which to assess the accuracy of routinely collected measurements recorded in the Personal Child Health Record (PCHR). The study population was a sub-sample of children from ALSPAC who had height/length or weight measured both at an ALSPAC clinic and in the PCHR within two months of the ALSPAC clinic. Since ALSPAC and PCHR measurements were taken at slightly different ages, and since young children grow rapidly, comparisons needed to take account of age differences of measurements. To allow for this, comparisons were made between standard deviation scores (sds) using the 1990 growth reference. The difference between sds from clinic and PCHR measurements was assessed. If PCHR measurements are accurate, a mean difference of zero could be expected, assuming most children will not cross centiles of the reference curves in the (maximum) two months between measurements. Differences between height/length and weight measurements were assessed at age four months (N = 345), eight months (N = 1051), 12 months (N = 139), 18 months (N = 649), 25 months (N = 183), and 43 months (N = 123). Differences were examined using summary statistics and Bland-Altman plots; predictors of the differences were explored using linear regression.
Results
Accuracy of the routinely collected measurements was generally good. For weight, all mean differences were less than 0.08 sds (e.g. mean sds differences: at 4 months 0.049, 95% level of agreement −1.07 to 0.97, at 12 months 0.0025, 95% level of agreement −0.77 to 0.76). For height/length, mean sds differences were somewhat bigger than for weight, but still generally small (e.g. mean sds differences: at 4 months 0.43, 95% level of agreement −2.16 to 1.29, at 12 months 0.16, 95% level of agreement −1.32 to 1.00). The observed differences were not strongly or consistently affected by child anthropometry, sex, social class, birth weight, birth length, or maternal anthropometry.
Conclusion
Routinely collected height/length and weight data appear to have generally good accuracy, supporting their use in both clinical practice and research.
