7 measurements are therefore as good as are likely to be obtained. It will therefore be assumed in these comparisons that the household surveys represent the "true" malnutrition rate.

20. For 1985 and 1989 the survey and clinic data are both for children under 36 months of age. The number of observations used from the surveys were as follows: in 1978, 2007; in 1985, 3332; in July 1989, 509; and in November 1989-January 1990, 964. The confidence interval calculated for the WHO standard combined moderate and severe low weight-for-age malnutrition rates were all about plus or minus 1.5 percentage points around the estimate.

21. The 1978 survey tabulb:ions provide information by parish and by age, but not by both simultaneously. Of necessity, survey observations are used for all children under 60 months in the seven parishes to which the clinic data correspond. For the fourteen parishes together, the difference between the combined Gomez grades I-III for children 0-59 months and for children 0-35 monthz was only 3 percent or 1 percentage point, so comparisons should be reasonably valid.

22. Although the household surveys and clinics report weights for children of the same age range, the distribution of children in that range may be different. Clinic attendance is usually most frequent among the youngest children. Vaccination norms, for example, would prompt three visits in the first six months of life, one visit between six and twelve months and one visit between twelve and eighteen months. Malnutrition rates are lowest in the first six months when breastfeeding is a main source of nourishment, and then peaks for 12-23 month olds after weaning. The distribution of children by ages of tLae clinic attenders will therefore influence the estimate of malnutrition rates. Properly, clinic data should be adjusted to prevent any biases of this sort from confusing comparisons with the household data. Unfortunately, the Jamaican clinic data are not tallied by age group so the comparison will be made with unadjusted clinic data.

23. The Comparison. In all fcur cases, the clinic data underestimated the malnutricion rate (see Tables 2 and 3). In three cases the clinic-based estimate fell outside the confidence interval for the survey-based estimate. In 1978 and 1985, using the Gomez classification, the combined rate of grades II and III was underestimated by clinic data by 37 and 47 percent, respectively. In 1989, WHO standards were used. For the combined moderate and severe categories, the clinic data underestimate malnutrition by 34 percent in the third quarter, but only 8 percent in the fourth quarter.

24. The degree of discrepancy between the clinic and survey estimates is very sensitive to the measure used in the comparison. In the first quarter of 1985 (1985-QI), for example, the clinic-based rate underestimates malnutrition as defined by the combined Gomez grades II and III by 47 percen.. However, malnutrition as defined by Gomez grade I is underestimated by 2f. percent. Malnutrition as defined by Gomez grade II is underestimated by 45 percent. The extent of adequate nutrition is overestimated by 19 percent. In general, the degree of underestimation of clinic-based malnutrition Lates is higher for more serious forms of malnutrition.