Verifying a legacy macroprolactin assay in an NHS biochemistry laboratory

I suspect we’ve all had one of those uncomfortable moments in our careers. The kind where a small but irritating problem quietly lands on your desk. Nobody really understands it, nobody particularly wants to deal with it, but somehow it has become your problem. It’s your section, your responsibility, and saying “no” isn’t really an option.

For many NHS biochemistry laboratories, macroprolactin testing falls squarely into that category. It is rarely anyone’s favourite assay. The method has often been in use for years – sometimes decades. Staff perform it because that’s how it has always been done, the rationale has faded into folklore, and nobody quite remembers from where the protocol came.

Biomedical scientists, accustomed to highly automated analysers processing hundreds of samples an hour, tend to view a manual polyethylene glycol (PEG) precipitation with all the enthusiasm usually reserved for performing monthly analyser maintenance. Support workers quite rightly point out that the dilutions and interpretation often fall outside their scope of practice. The task frequently finds its way to assistant practitioners, who perform it diligently but are unlikely to nominate it as the highlight of their working day.