MPH Master pieces

Risk adjustment and outcome comparisons

When a hospital (or a surgeon) has a high death rate, the first response is "but we treat sicker patients". At which point risk adjustment is called for.

Risk adjustment is basically a multiple regression analysis, with 'place of treatment' as the predictor of outcome, and everything else as a confounder. The 'everything else' in a risk adjustment is a set of indicators of severity (risk of death). That's ok if your measure of risk is something very objective such as blood pressure but it's not ok if you pick a measure such as '%age of patients admitted as an emergency'.

At first sight, it seems obvious that hospital A, where most patients are admitted as emergencies, must be treating sicker patients than hospital B, where there are few emergency admissions. But there is a problem: policies on emergency admission may differ. So the data item 'emergency admission' does not mean the same in both hospitals (whereas blood pressure 100/60 does). You can't use emergency admission in risk adjustments.

Here is an interesting worked example of all this using real data. The statistical warning sign is that a predictor (emergency admission) signifies a higher risk of death in hospital B than hospital A. The predictor carries a different meaning or value in the different places, so technically this is an interaction between the two predictors.  

Moral: Don't measure something till you understand it thoroughly. (Kelvin famously thought the opposite!)

Tobacco control - harm reduction or zero tolerance?

Here is an interesting exchange of views on tobacco control. Note that with questions like this there is little evidence and plenty of assertion!

A heavyweight team from the UK argue that we need to treat smoking like other addictions and go for harm reduction with 'MN' - medicinal nicotine. Commentators from Australia, India and Hong Kong are not convinced.

What do you think?

Lay advisers and condom use

I liked this study which focussed on increasing condom use in young (18 - 29yrs) African-American men newly diganosed with a sexually transmitted disease. The research team 'selected, hired and trained'... ;a young African-American male who had grown up and resided in the main catchment area served by the clinic'. They had taken a year to develop the intervention and, wisely in my view, didn't offer it to men who never used condoms - that would have been a bridge too far. They focussed on getting men who already used condoms to some extent to use them correctly and consistently.  And as a revealing comment, the questionnaires were recorded onto a CD to avoid 'problems associated with low literacy'.

Outcomes included condom use and number of sexual partners (self reported) but also number of new infections as judged by medical record review. No economic analysis which is a shame but overall a interesting piece of research. Didn't try to do too much and achieved what it set out to do in a famously difficult area of behaviour change.