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MedGenMed. 2005 Nov 29;7(4):56.

Misdiagnosis of overweight and underweight children younger than 2 years of age due to length measurement bias.

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  • 1Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts, USA.



Accurate determination of the length of very young children is important because weight-for-length standards are used to assess both under- and overweight. Clinical measurements of length, which usually involve a paper-and-pencil method, may often be inaccurate in children younger than 2 years.


To compare length measured by the conventional clinical paper-and-pencil method with length measured by the research standard recumbent length-board method in a sample of children under 2 years of age.


Research assistants measured 160 children 0 through 23 months of age using the recumbent length-board method, and clinical staff measured the same children using the paper-and-pencil method. To assess the relationship between the research and clinical length measurements, we used ordinary least squares regression.


We found a strong linear relationship between the 2 measures of length (R2 = 0.98). The paper-and-pencil method systematically overestimated length in children under 2 years of age. A fitted regression equation estimated that the research standard length was 95.3% of the clinical measurement plus 1.88 cm. Over the entire age span, the mean (SD) difference between clinical and research measurements was 1.3 (1.5) cm.


Using the paper-and-pencil method can lead to underestimates of overweight and exaggerated estimates of thinness. To improve the accuracy of length measurement, medical providers should use standardized procedures with a recumbent length board to measure children under 2 years of age, at least for children whose initial paper-and-pencil measurement of length puts them at one extreme or the other.

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