I read the two letters from McCaughey and Curry and their respective colleagues^1,2 with astonishment. Their debate on a policy for electron microscopy (EM) use reminded me of those mediaeval ones about the number of angels that could dance on the head of a pin. Interesting debate, pity it missed the point. They failed, I think, to address three important aspects:J Clin Pathol 2000;53:722–725

1. The nature of virus diagnosis. No one can pretend that virus laboratories can investigate every individual “viral” illness in the community, but they have an obligation to monitor what is prevalent in it. Although attractive to a cash strapped service, selecting specimens on the basis that some are more likely to yield positives than others misses the point of diagnosis—more than one virus can cause many “virus like” syndromes and virus excretion does not parallel exactly the presence of symptoms. To discard specimens taken from those who are recovering because the yield may be low, or where the cause is apparently obvious, strikes me as arrogant. If someone has taken the trouble to send a specimen, it seems reasonable to look at it, if only in the hope that the sender might be encouraged to send others in the future, especially if it turns out to be positive. It is a constant battle to get worthwhile virological specimens sent to the laboratory—choking them off is daft. Moreover, I would further confirm the Irish view that solid stools may often yield positives and also that making the diagnosis by holding the specimen up to the light (metaphorically speaking) is very unrewarding. Trends in infection can only be given some credence if the specimen base remains more or less constant. Arbitrary and variable selection of what will be examined, and what will not, destroys this base. …