Sir.—The article by Ellerstein and Ostrov1 in the February 1985 issue of AJDC provides useful information on the duration of diagnostic hospitalization for children with failure to thrive because of caloric deprivation. The authors also proposed a system for evaluating weight gain in infants with failure to thrive. To this effect, they derived a "growth quotient," which is the mean weight gain of the observed infant divided by the mean weight gain at the fifth percentile of a reference population matched for age and sex. This mathematical calculation shows improvements in weight velocity, particularly in the older infants and children, which a cursory inspection of daily weight gains might not have shown as clearly.
The choice of weight gains at the fifth percentile as the standard of comparison will usually result in growth quotient values higher than what might be observed if the infant's expected growth pattern is