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Public Health Dispatch: Manufacturer's Recall of Rapid Assay Kits Based on False Positive Cryptosporidium Antigen Tests --- Wisconsin, 2001--2002

The Wisconsin Division of Public Health and the Wisconsin State Laboratory of Hygiene (WSLH) reported that a recent cluster of cryptosporidiosis cases in a three-county area in southeastern Wisconsin was the result of false-positive tests. During December 1, 2001--February 1, 2002, approximately 30 cases of cryptosporidiosis were diagnosed at a laboratory in southeastern Wisconsin using the Becton, Dickinson, and Company (Franklin Lakes, New Jersey) ColorPACTM Cryptosporidium/Giardia rapid assay (lot number 219370, expiration date 2002-06-05). Seventeen stool specimens, which were collected from 11 patients and tested positive by the rapid assay, were re-evaluated at WSLH. Six of these stool specimens were in EcoFix (Meridian Bioscience Inc., Cincinnati, Ohio), eight were in Cary-Blair transport media, and three were formalin fixed. All 17 specimens tested negative for Cryptosporidium at WSLH using the hot safranin stain and MeriFluor (Meridian Bioscience Inc., Cincinnati, Ohio) Cryptosporidium/Giardia direct fluorescent antibody kit with concentrated specimens.

For comparison, WSLH repeated the rapid assay tests of the specimens using Becton, Dickinson, and Company ColorPACTM Cryptosporidium/Giardia rapid assay from the same lot used at the southeastern Wisconsin laboratory. Eleven (65%) of the 17 stool specimens were positive on repeat testing, including five (83%) specimens in EcoFix, four (50%) of specimens in Cary-Blair transport media, and two (67%) of the formalin-fixed specimens. The ColorPACTM kits also were used to test four known Cryptosporidium negative stool specimens, and two of these tests were positive. Becton, Dickinson, and Company has voluntarily recalled this lot from laboratories.

Reported by: T Haupt, MS, JP Davis, MD, Wisconsin Div of Public Health; D Warshauer, PhD, Wisconsin State Laboratory of Hygiene. M Beach, PhD, S Johnson, MS, Div of Parasitic Diseases, National Center for Infectious Diseases; D Croft, MD, EIS Officer, CDC.

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