Rationalised virological electron microscope specimen testing policy

Curry et al have produced guidance on the provision of electron microscopy testing in virus laboratories.1 Such local guidance is necessary to make expensive and time consuming diagnostic services such as electron microscopy cost-effective and clinically useful.

In their report they state that “specimens for electron microscopy examination should be unformed faecal specimens (not formed stools...)”. They justify this approach by reference to “...20 years of experience have shown (unpublished results) that these are more productive.” Effectively they reiterate the commonly accepted assumption that viruses of gastroenteritis are more likely to be found in liquid than in solid faecal specimens.

Our findings do not support this dogma.2 We examined 2568 specimens by electron microscopy. A virus was demonstrated in 8.6% of liquid, 19.9% of semisolid, and 25.2% of solid specimens (χ² for linear trend, p < 0.0001) This observation was valid for both adenovirus (2.4%, 5.0%, and 6.6%) and rotavirus (5.2%, 13.6%, and 16.6%). Curry et al cite our study but consider that their impression (unpublished results) of 20 years experience is better evidence than our data. This is contrary to an evidence based approach. Curry and his …