Objective To test whether different measuring techniques produce systematic differences in head size that could explain the large head circumferences found in Northern European children compared with the WHO standard.
Design Cross-sectional observational study.
Setting Scotland, UK.
Patients Study 1: 68 healthy children aged 0.4–18 months from mother and baby groups and a medical students teaching session. Study 2: 81 children aged 0.4 to 25 months from hospital wards and neonatal follow-up clinics.
Interventions Study 1: heads measured with plastic tape using both the WHO tight and UK loose technique. Study 2: heads measured using WHO research technique and a metal measuring tape and compared with routinely acquired measurements.
Main outcome measures Mean difference in head z-scores using WHO standard between the two methods.
Results The tight technique resulted in a mean (95% CI) z-score difference of 0.41 (0.27 to 0.54, p<0.001) in study 1 and 0.44 (0.36 to 0.53, p<0.001) in study 2. However, the mean WHO measurements in the healthy infants still produced a mean z-score that was two-third of a centile space (0.54 SD (0.28 to 0.79) p<0.001) above the 50th centile.
Conclusion The WHO measurement techniques produced significantly lower measures of head size, but average healthy Scottish children still had larger heads than the WHO standard using this method.
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Contributors CMW conceived the study, was a measurer in study 1, undertook the analysis and drafted the paper. SL planned and ran the data collection for study 1 and was a measurer. MB planned and ran study two and collected the outpatient measurements. JDS helped plan study 2 and draft the paper. All authors have seen and approved the draft paper. Study 1, round A was undertaken as an MSc summer project and study 2 as an intercalated BSc project.
Competing interests CMW led the group that implemented the WHO head standard into growth charts in the UK.
Ethics approval Ethical approval study 1: Glasgow University MVLS College Ethics Committee. Study 2: NHS West Midlands—Black Country Research Ethics Committee 15/WM/0474.
Provenance and peer review Not commissioned; externally peer reviewed.
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