Corrected data on antidepressant prescribing

PHARMAC has completed further analysis of data on the prescribing of antidepressants, and revised down very considerably the numbers of preschool children being prescribed antidepressants.

In its re-analysis, PHARMAC cross-referenced data using National Health Index (NHI) numbers with prescriptions coded by patient category (age bands). The result indicates that the previous dataset had over-reported the number of children prescribed antidepressants.

PHARMAC Medical Director Dr Peter Moodie says that overall, the two sets of codes for age matched one another 99.6% of the time. However, while small in percentage terms, this 0.4% discrepancy had a very large impact on our analysis of the small subset of prescriptions for young children.

“Re-examination of the data shows a picture more in line with what we would expect in clinical practice,” says Dr Moodie. “A very, very small number of pre-school children do appear to be prescribed antidepressants, and this is a far more acceptable pattern.” 

Removal of the miscoded records results in the new estimates erring more on the side of caution and probably under-estimating the total numbers of children.

“It’s now clear that we made an error in interpreting the figures for preschoolers and are sorry for that.  We now realise the impact a small coding error, which could have been made at a number of levels of data entry, can have on accuracy when small numbers of prescriptions are involved.”

While openly acknowledging the error, PHARMAC is reassured that overall the data is robust.

The revised figures show:

That 91 prescriptions could be identified for preschool children and none of them were in the 0 to 1 year olds. Assuming one prescription is written each month, this would translate into less than 10 children under 6 receiving antidepressants in the 2006-07 year.
Approximately 14,000 prescriptions were written for children between the ages of 6 and 17 which is consistent with the original figures.
The number of prescriptions written overall for anti-depressants remains confirmed at 1.125 million for the 06/07 year.

PHARMAC will be sharing its learnings from this experience with the Ministry of Health, who gather data on prescriptions and other health information.

ENDS

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