[A comparative study of coprological methods for identifying Cryptosporidium spp. oocysts]

With a view to optimize the etiological diagnosis of diarrhoea the authors have attempted to improve the diagnostic methodology for the parasite Cryptosporidium spp. as a current general technique, as well as a screening technique. A comparative evaluation of the various methods used for the concentration and the staining of cysts of Cryptosporidium spp. was done after quantification according to a five parameter score: electiveness, morphology, chromatic contrast, rapidity and accessibility. The importance of the screening tests in the diagnosis of cryptosporidiosis was evaluated according to indicators such as sensitivity, specificity and predictive value. The maximal general score (17) was obtained with the modified Ziehl-Neelsen stain which was both sensitive and viable, and was used as a method for the confirmation of the presence of the parasite. With regard to the screening methods rapid techniques employing methylene-blue and/or fuchsine gave indicator values between 76% and 83%. The best results were obtained when samples were enriched with the aid of concentration techniques. It is appreciated that the concomitant and repeated use of two techniques of diagnosis, a rapid one and a confirmation technique aimed at demonstrating the presence of Cryptosporidium cysts allows a competent parasitological diagnosis of cryptosporidiosis.