EFFECT OF FECAL CONSISTENCY ON VIROLOGICAL DIAGNOSIS

A study was set up to investigate the effect of consistency of routine faecal specimens on the diagnostic yield by electron microscopy (EM) and virus isolation. A total of 3078 specimens were characterized as s olid, semisolid, or liquid. Of 2568 specimens processed by EM a virus was demonstrated in 8.6% of liquid, 19.9% of semisolid and 25.2% of so lid specimens (Chi-squared for linear trend, P value <0.0001). This ob servation was valid for both adenovirus (2.4%, 5.0% and 6.6%) and rota virus (5.2%, 13.6% and 16.6%). Virus isolation was positive in 3.6% of liquid, 17.4% of semisolid and 18.1% of solid specimens. (Chi-squared for linear trend, P value <0.0001). We suggest that solid faecal spec imens at the end of an episode of diarrhoea will have a higher diagnos tic yield than liquid specimens at the peak of symptoms. Our findings repudiate the commonly held dogma that viruses of gastroenteritis are more likely to be found in liquid than in solid faecal specimens. This finding has important implications for those establishing diagnostic algorithms for the investigation of viral gastroenteritis.