Comparative evaluation of direct stool smear and Formol-ether Concentration Methods in the identification of Cryptosporidium species

Abstract

Cryptosporidium is a common cause of diarrhoea in patients with Human Immunodeficiency Virus (HIV)/Acquired Immunodeficiency Syndrome (AIDS). Unfortunately this pathogen is not often checked for in Microbiology laboratories because the formol-ether stool concentration method for identification of Cryptosporidium is cumbersome and may not be routinely undertaken in very busy laboratories and in laboratories with inadequate personnel. This study was therefore carried out to compare the outcome of direct stool examination and formol-ether concentration method with the aim of finding a non-cumbersome method of examining for Cryptosporidiumspecies routinely in stools when it is indicated. Fresh stool specimens of 193 HIV positive and 200 HIV negative patients (control) attending clinic at the Lagos University Teaching Hospital (LUTH) were processed within two hours of collection using direct stool smear and formol-ether concentration methods. Permanently stained slides were prepared using Kinyoun acid-fast stains. Cryptosporidium oocysts were found in 35 (18.1%) of HIV seropositive patients using direct stool smear method and in 36 (18.7%) using formol-ether concentration method. There was no statistical difference between the two methods (p > 0.05, xz = 0.012, df = 1 at 95% confidence limit critical ratio = 3.841). No Cryptosporidiumwas identified in the control (HIV negative) patients using either method. Cryptosporidium oocysts can be routinely checked for in the Microbiology laboratories using either direct stool smear or formol-ether concentration stool method with comparable sensitivity.

KEY WORDS: Cryptosporidium identification, direct stool smear, concentration method.

Nigerian Journal of Health and Biomedical Sciences Vol.4(1) 2005: 5-7