[External quality control of the parasitological diagnosis of Cryptosporidium parvum]

Between 1991 and 1994, eight external quality assessments of Cryptosporidium parvum infection diagnosis were performed. Stool specimens were sent to 74 laboratories, to be stained and examined. In 40 laboratories (54.1%), the diagnosis was correct in all evaluations, whereas in 34 (46%), the diagnosis disagreed with the parasitology reference laboratory in one occasion or more. The mean correlation of diagnoses with the reference laboratory was 88% (range 79-96%). Ninety-three percent of negative samples and 87% of positive samples were correctly diagnosed. These figures are similar to those obtained abroad. These results lead to the development of a quality control network for the diagnosis of Cryptosporidium parvum infections along the country, aiming to improve its reliability.