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Centre for Evidence-
Based Medicine

Completed Prognosis Worksheet for Child Health

Clinical Question

Would grommet surgery reduce the likelihood of behavioural problems later in childhood?

Are the results of this prognosis study valid?

  1. Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease?
    Yes. Large birth cohort of more than 12,000.
  2. Was patient follow-up sufficiently long and complete?
    Maybe. Follow up was for 10 years. Original number stated as more than 12,000, at 5 years about 12,000 and at 10 years about 9,000. Authors comment that the prevalance of middle ear disease was similar in children followed as in those lost to follow up but no figures given.
  3. Were objective outcome criteria applied in a "blind" fashion?
    Yes. Scales for behaviour and cognitive ability based on parent and teacher responses to questions. Respondents were not necessarily blind to middle ear disease but many factors were studied, and therefore, unlikely to be affected.
  4. If subgroups with different prognoses are identified, was there adjustment for important prognostic factors?
    Yes. Adjustment for social class and maternal malaise, but may be incomplete. No other social or cultural factors, such as maternal age or education, taken into account.
  5. Was there validation in an independent group ("test-set") of patients?
    No, but previous cohort studies have reported a possible association.

Are the valid results of this prognosis study important?

  1. How likely are the outcomes over time?
    Look at risk of neurotic behaviour score greater than 90th percentile at 10 years for children with hearing difficulty based on parent reports (table 9). OR= 1.40 and for teacher reported behaviour (table 10) OR= 1.25

    However, using continuous variables, the largest difference was for antisocial behaviour, with a 0.13 SD difference at 10 years. This is small, and unlikely to be clinically important.
  2. How precise are the prognostic estimates?
    Can look at 95% confidence intervals around the odds ratio. CI around OR does not include 1 so result is statistically significant.

    OR for Hearing Difficulty = 1.38 (1.1 to 1.73)
    OR for Ear Discharge = 1.42 (1.17 to 1.73)

Can you apply this valid, important evidence about prognosis in caring for your patient?

  1. Were the study patients similar to your own?
  2. Will this evidence make a clinically important impact on your conclusions about what to offer or tell your patient?
    Yes. Magnitude of effect is small but there is an association. Not enough information to discuss surgery as no evidence that intervention will alter long term risks.

Additional Notes

  1. Health visitor would probably advise mother to inform school when her son has ear discharge or hearing difficulty, so teachers make an extra effort.
  2. Surgery has not proven to reduce the behavioural or cognitive problems associated with glue ear, so cost of private surgery probably not warranted without more evidence.
  3. The small difference in behaviour may nevertheless be important at a population level.
  4. There is some suggestion of an interaction between social class and the effects of glue ear on behavioural and cognitive problems.

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