135 Body composition measurement methods in preterm infants 7 Study eligibility criteria Studies were included if they reported on body composition measurement in infants born before 37 weeks of gestation. The body composition measurement had to take place between birth and 6 months corrected age. Studies needed to evaluate methods which measure or estimate fat (-free) mass in (kilo)grams or percentage. Studies measuring or estimating total body water (TBW) were also included. See table 2 for a description of the included methods 12,13. In addition to validation studies, randomized controlled trials, cohort studies and epidemiologic studies where included if they reported the accuracy or predictive values of body composition measurements. Definitions Amethodwas deemed validated if themethod showed good statistical agreement to a reference method. Currently there is no golden standard for the measurement of body composition. Hence, studies of all possible reference methods were accepted. Good agreement was defined as amaximumallowed difference of 10% of themean value of the body composition parameter in the study population. For example, if the mean of the fat free mass in a study population was 2000 g, then the bias + limits of agreement had to be smaller than + 200 g. For studies where agreement was not assessed, effect size of the different methods was determined by the r-squared value. A value below 0.5 was considered a poor predictive value, 0.5 to 0.7 as a moderate predictive value and > 0.7 was considered as good predictive value.14 Data extraction Two reviewers (D.F.J.Y. and D.d.J.) separately screened the studies, initially based on title and abstract, followed by full text review of relevant studies.
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