Measured height and height estimated from body segments in hospitalised adults in Bloemfontein, South Africa
Williamson, Hanna Eugenie
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Background and motivation: Accurate height measurement is essential in the assessment of the hospitalised patient, amongst others, to screen for malnutrition or risk of malnutrition, which negatively affects morbidity and mortality. Height is also used to calculate nutrition requirements, adjust drug dosages and predict lung volumes, muscle strength and glomerular filtration rate. The gold standard is measuring standing height with a stadiometer using a standardised technique. In the hospital setting, however, patients often cannot stand up straight and unassisted for accurate height measurements according to the standardised technique. Globally, several equations predicting height have been standardised on various populations; none have been developed specifically for the general or hospitalised South African population. Methods: This study investigated the agreement and association between directly measured (reference) height, and self-reported height, height recorded on admission in the medical files, recumbent length, and height estimated by indirect methods based on body segment measurements (, demi-span, ulna length, knee height, tibia length, fibula length, and foot length) in three public hospitals in Bloemfontein, South Africa. Bland–Altman analysis was used to assess the 95% limits of agreement between the height predicted from published estimate equations and reference height. Spearman correlations and multiple regression analysis were used to identify the body segment that best predicted height in this population. Results: Less than 5% of 141 participants (61.7% male; median age 38.8 years [interquartile range: 10.1 years] could self-report their height, and, although stadiometers were available in all the wards, only 16% had height recorded in their medical files. Healthcare practitioners, thus, did not seem to consider the measuring and recording of height as a priority. Eleven published equations developed for adults <65 years (and standardised for gender), based on various upper and lower body segments, were tested. Only a set of equations standardised for males and females, and black and white ethnicities, by Chumlea et al. (1994) on 5415 healthy adults <60 years in the United States, yielded predicted heights that did not significantly differ from the reference height measured in this study (95% CI; -0.9; 0.2) (95% limits of agreement indicating that, in 95% of cases, height was underestimated by 5.8 cm to overestimated by 7.2cm). Knee height also correlated the strongest with height in both genders (males: R2:0.77; females R2:0.86; p<0.0001) and was identified by multiple regression analysis as the best predictor of reference height. Foot length and ulna length showed the weakest correlation with reference height and performed weakest in the regression analysis. Recumbent height, measured strictly according to the standardised technique, differed significantly from reference height, but yielded 95% limits of agreement indicating that, in 95% of cases, the recumbent length only underestimated height by 4.0 cm to overestimated height by 1.3 cm. Conclusions: Clinical studies commonly suggest that body segment-based equations for predicting height, need to be standardised for each population, and suggested ethnic differences as the reason. The findings of this study, however, support evidence from forensic science, anthropology and growth studies that environmental stresses, including disease load and dietary niche, influence the development and growth of the various long bones in ways that affect the body proportions. This developmental plasticity differs across different body segments, causing lower limb length to show a greater proportionality to height. Relative leg growth is accelerated during the early years of life; thus, stunting seems to have a more pronounced effect on the length of the lower leg long bones. Thus, the high prevalence of stunting among South Africans may explain why knee height, outperformed upper body measurements in this population of patients admitted to public hospitals in a South African city. Recommendations: Health care practitioners should be educated on the importance of accurately measuring height, especially as an integral part of screening for malnutrition or those at risk of malnutrition. More extensive studies across different South African populations are needed to confirm the findings, better the current understanding of the effects of environmental stressors on body proportion, and to develop accurate height- prediction equations that may be used in South African populations. Stunting in South Africa should also be addressed.