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Editor,—I was surprised to read in Raynoret al's recent paper1 the statement that their study was “the largest randomised controlled trial on children with failure to thrive in this country”. Our trial studied nearly three times as many children and was published four months before their paper was accepted.2
Did they think that it was not a true trial? It conformed to CONSORT guidelines,3 with random allocations to treatment, and all patients recruited prospectively (not retrospectively as they suggest). Did they feel the children did not have true failure to thrive? They suggest that our study included “many children who . . .proved to be small or to have temporary growth faltering”. Eighty per cent of the cases identified in our study had persistent failure to thrive and, as they were identified solely on the basis of slow postnatal weight gain, the contribution of constitutional short stature will have been much less than in Raynor et al's study where low centile position alone was used as one of the entry criteria.
Much of Raynor et al's paper and Blair's accompanying commentary dwells on the “mystery” of why the intervention did not show a significant effect. In fact, with only about 40 children in each arm they had little hope of detecting anything other than a very large treatment effect (80% power, p = 0.05 to detect difference of 0.85 SD score). This which would be unlikely when both groups were offered some sort of active treatment. In our study, with subjects followed up for twice as long and up to half of the control children completely untreated, we had only a 40% chance of detecting the significant treatment effect (0.28 SD) that we in fact found.
If the condition of interest is failure to thrive, where referral reflects concern about growth or weight gain, the main outcome must be a measure of growth, whoever is delivering the intervention. The solution to the problem of measuring the effectiveness of health visiting is not to argue for some new measure but to conduct trials of sufficient size to have some realistic hope of success.
Dr Rudolf comments:
At the time of writing our article Wrightet al's study had not yet been published. The reference to our study being the largest in this country was inadvertently left in when we subsequently revised the article for publication. However, Wright's comments do allow us to highlight the differences between these two studies on health visitor intervention for failure to thrive.
The first relates to the two populations of children studied. The Newcastle children were selected by weight screening alone, whereas the Leeds children were included only on receiving a clinical diagnosis of failure to thrive. We contend that “weight faltering” is a more appropriate term for those showing poor growth alone, and that “failure to thrive” should be reserved for children where there are associated psychosocial or emotional issues. This is of course not just semantics. Wright's own recently published work1-1 suggests that the intellectual and growth risks are low in children identified by weight screening alone.
The second difference regards the intervention itself. The Leeds children received intensive individualised help from a highly experienced health visitor with special training in assessment, counselling, and nutrition. In comparison, the Newcastle health visitors' training consisted of only a few hours and the intervention was often only one or two visits. Why there is such a discrepancy in the results, given the relative difference in intensity of the interventions, is not entirely clear.
We noted that our study numbers were small, although 83 children is a sizeable sample from any single clinic. It is unlikely that any one centre can enrol enough patients using the strict clinical diagnosis outlined above, and I fully support Wright's contention that larger (almost definitely multicentre) studies are required to produce definitive results.
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