title: Nutrient balance studies in the preterm infant: crossover and parallel studies as methods of experimental design.
abstract: Crossover and parallel studies were compared as methods of experimental design during nutritional balance studies in the preterm infant. Twelve formula-fed infants (birth weight, 1,362 +/- 125 g, mean SD; gestational age, 32.3 +/- 1.7 weeks) were studied over 2 continuous weeks, "period" being the only obvious difference between the weeks. During each week, growth was determined, and 84-h nutrient balance was performed. Growth was adequate during both weeks. Increased absorption and retention (mg/kg/day and percent) of calcium and copper were noted during the 2nd week. Increased retention (mg/kg/day and percent) of phosphorus and magnesium was noted also, indicating increased nutrient assimilation due to a period effect. However, the variance due to the period effect (crossover) was less than that associated with "patient characteristics" (parallel study). In addition, sample size requirements were less, indicating that crossover studies are more efficient than parallel studies as a method of experimental design.
authors.affiliation: Department of Pediatrics, University of Tennessee, Memphis.
authors.forename: R J
authors.initials: RJ
authors.lastname: Cooke
authors.forename: F
authors.initials: F
authors.lastname: Perrin
authors.forename: J
authors.initials: J
authors.lastname: Moore
authors.forename: C
authors.initials: C
authors.lastname: Paule
authors.forename: K
authors.initials: K
authors.lastname: Ruckman
mesh_terms: D000704:Analysis of Variance; D001835:Body Weight; D004602:Elements / Q000378:metabolism; D006801:Humans; D007225:Infant Food; D007227:Infant Nutritional Physiological Phenomena; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development / Q000378:metabolism*; D011897:Random Allocation; D012107:Research Design
chemical_list: D004602:Elements