Clinical and Analytical Evaluation of a Single-Vial Stool Collection Device with Formalin-Free Fixative for Improved Processing and Comprehensive Detection of Gastrointestinal Parasites.

Microscopic examination of feces is a standard laboratory method for diagnosing gastrointestinal parasite infections. In North America, the ovum and parasite (O&P) examination is typically performed using stool that is chemically fixed in polyvinyl alcohol (PVA) and formalin, after which the stool is concentrated by filtration to enhance sensitivity. Mini Parasep solvent-free (SF) tubes allow collection and concentration within a single collection vial. The goal of the study was to determine whether consolidated processing and concentration with the Parasep tubes using an alcohol-based fixative (Alcorfix) provide O&P examinations equivalent to or better than those done by processing of PVA-formalin-fixed stool using a SpinCon concentration device. Parasep tubes revealed filtration performance equivalent to that of the SpinCon concentration device using PVA-formalin-fixed stool containing protozoa. Specimens cocollected in Parasep tubes containing PVA-formalin and Alcorfix revealed comparable morphology and staining for various protozoa. Alcorfix effectively fixed live Cryptosporidium and microsporidia such that morphology and staining were conserved for modified acid-fast and modified trichrome stains. A work flow analysis revealed significant time savings for batches of 10 or 30 O&P specimens in tubes with Alcorfix compared to the amount of time that it took to analyze the same number of specimens in tubes with PVA-formalin. The direct hands-on time savings with Mini Parasep tubes were 17 min and 41 s and 32 min and 1 s for batches of 10 and 30 specimens, respectively. Parasep tubes containing Alcorfix provide significant work flow advantages to laboratories that process medium to high volumes of O&P specimens by streamlining processing and converting to a single tube. These improvements in work flow, reduction of the amount of formalin used in the laboratory, and equivalent microscopy results are attractive advancements in O&P testing for North American diagnostic parasitology laboratories.

Stool Reducing Sugars and Stool pH Are Poor Screening Tests for Intestinal Disaccharidase Deficiencies in Children.

BACKGROUND: Tests for stool reducing sugars and stool pH are ordered for children with osmotic diarrhea to screen for carbohydrate malabsorption. METHODS: We compared the results of the two screening tests, stool reducing sugars and stool pH, with a more definitive result from an intestinal tissue disaccharidase activity assay ordered for pediatric patients (<18 years old). Overall, 159 patients had results for tissue disaccharidase and stool reducing sugars, but only 115 had additional results of stool pH. Forty-six of the 159 patients had mild, moderate, or severe disaccharidase deficiencies. The sensitivity and specificity of the screening tests were calculated for individual disaccharidase deficiencies. In addition, trends of abnormal tissue disaccharidase, stool reducing sugars, and stool pH results were examined in different age groups. RESULTS: The sensitivities for stool reducing sugars and stool pH were 9% to 28% and specificities were 74% to 81% for individual disaccharidase deficiencies. Infants (0 years of age) had the highest percentage of abnormal results across all three tests; however, the positive predicative values were 54% and 50% for stool reducing sugars and stool pH, respectively. CONCLUSIONS: The screening tests, stool reducing sugars and stool pH, had low sensitivity compared with results of measured tissue disaccharidase activity in pediatric patients. Infants had the highest percentage of abnormal results for all three tests, but the screening tests still performed poorly in that age group. This study suggests that stool reducing sugars and stool pH should not be used as screening tests for carbohydrate malabsorption due to disaccharidase deficiencies in pediatric patients.