Fecal specimen collection

The numbers and times of collection for fecal specimens depend somewhat on the diagnosis suspected. As a routine, because some organisms are shed in a variable pattern, it is advisable to examine multiple specimens before excluding parasites. The general recommendation is to collect a specimen every second or third day, for a total of three specimens. From a hospitalized patient, one specimen each day for three days may be more cost effective. 

The present authors have developed procedures for collection and storage of urine and fecal specimens as follows 24 h urine specimens are collected in plastic containers (Scientific Products, McGraw Park, IL) and the total volume is recorded. A 10 mL aliquot is transferred to a polypropene tube (Falcon, Oxnard, CA) which is stored at 4°C. 

Fecal specimens are collected directly into plastic bags which are weighed at the end of a 24-h time period, placed in a paper container and frozen. 

A fecal portion of a few grams should be collected without additive. Specimens should be stored in a dark container, preferably in the cold. Storage of more than 2 days should be at -20°C. 

A metabolic bed is used to collect timed specimens from infants. The infant lies on a fine screen above a funnel-shaped base contahiing a drain under which a container is placed to receive urine. The fine screen retains fecal material. Nevertheless, the urine is likely to be contaminated, to some extent, by such material. 

In adults, measurement of fecal nitrogen and fat in 72-hour specimens is used to assess the severity of malabsorption measurement of fecal porphyrins is occasionaEy required to characterize the type of porphyria (see Chapter 32).UsuaEy, no preservative is added to the feces, but the container should be kept refrigerated throughout the coEection period and care should be taken to prevent contamination from urine. When the collection is complete, the container and feces are weighed, and the mass of excreted feces is calculated. The specimen is homogenized and ahquotted so that the amount of fat or nitrogen excreted per... 

Balance studies involving aluminium make it necessary to perform fecal analysis. A recent report for the authors laboratory describe methods of collection, shipping and analysis of these types of specimens (Brown et al., manuscript in preparation). 

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