Background: Our aim was to determine the diagnostic value of electron microscopy in evaluating the etiology of gastrointestinal disease in patients infected with the human immunodeficiency virus (HIV).
Methods: A retrospective review of electron microscopic and light microscopic results of all HIV-positive patients with gastrointestinal and liver diseases was made during a 3-year period from June 1995 to June 1998.
Results: A total of 145 HIV-positive patients had their electron microscopy specimens reviewed. Of these, 136 were investigated for diarrhea, and the other 9 for increased liver enzymes. Twenty-seven of the 145 (18.6%) HIV-positive patients had a pathogen identified by electron microscopy, compared with only 13 of 145 (9%) identified by light microscopy (P < 0.005). The sensitivity of light microscopy for detecting opportunistic pathogens was 68%. Twenty-one of the 27 (77.8%) patients diagnosed by electron microscopy had microsporidiosis, and the most commonly diagnosed species was Enterocytozoon bieneusi. Light microscopy failed to identify 12 cases of microsporidiosis and 2 cases of leishmaniasis.
Conclusions: Electron microscopy contributes substantially to the identification of pathogens in HIV-positive patients. Light microscopy failed to identify one of every two pathogens diagnosed by electron microscopy.