Specimen fecal

TABLE 1.1 INCIDENCE OF INTESTINAL PARASITES IN 322,735 FECAL SPECIMENS EXAMINED BY STATE HEALTH DEPARTMENT LABORATORIES... 

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. 

A number of substances may interfere with stool examination. Particulate materials such as barium, antacids, kaolin, and bismuth compounds interfere with morphologic examination, and oily materials such as mineral oil create small, refractile droplets that make examination difficult. Antimicrobial agents, particularly broad-spectrum antimicrobial agents, may suppress amebae. If any of these substances have been used, specimens should not be submitted until the substances have been cleared (generally 5 to 10 days). A fecal specimen may appear satisfactory by gross examination when there is still barium, etc., which can interfere with microscopic examination. 

The fixative system generally used is a two-vial technique with one vial containing 5 to 10% buffered Formalin and the other vial containing polyvinyl alcohol (PVA) fixative. A portion of the specimen is added to the fixative in a ratio of approximately 3 parts fixative to 1 part specimen and thoroughly mixed to ensure adequate fixation. An alternative to Formalin is Merthiolate-iodine-formaldehyde (MIF), which fixes and stains at the same time. If unfixed specimens are processed in the laboratory, fecal films may be prepared and immediately fixed in Schaudinn fixative. 

TABLE 1.3 LABORATORY EXAMINATIONS FOR VARIOUS TYPES OF FECAL SPECIMENS... 

Direct wet mounts are prepared by placing a small drop of 0.85% saline toward one end of a glass slide (2 by 3 in. [ca. 5 by 7.5 cm]) and a small drop of appropriate iodine solution (see below) toward the other end. With an applicator stick, a small portion of specimen (1 to 2 mg) is thoroughly mixed in each diluent, and a no. 1 cover slip (22 mm) is added. The density of fecal material should be such that newspaper print can be read with difficulty through the smear. The material should not overflow the edges of the cover slip. Grit or debris may prevent the cover slip from seating and may be... 

Comminute a fecal specimen about 1 cm in diameter in a tube (16 by 100 mm) half filled with tap water. Add additional water to within 1 to 2 cm of the top. 

Permanent stains of fecal smears are most needed for the detection and identification of protozoan trophozoites, but they are also used for the identification of cysts. Wet mounts of fresh feces, even with stains such as methylene blue, are not as sensitive for trophozoites and therefore do not substitute for permanent stains. It is sometimes difficult to identify cysts which are detected in wet mounts thus, for each specimen, regardless of consistency, it may be worthwhile to fix a portion in PVA fixative or to prepare two fecal films fixed in Schaudinn fixative so that permanent stains can be performed if needed. Permanent stains also provide a permanent record and are easily referred to consultants if there are questions on identification. 

A number of staining procedures have been described. Some stains, such as chlorazol black, require fresh specimens and are not widely used. A variety of stains for fecal smears preserved by Schaudinn or PVA fixative have been described, including various hematoxylin stains. The stain most widely used in the United States is the Wheatley trichrome stain, which is the only permanent stain described in this chapter. The trichrome staining procedure uses reagents with a relatively long shelf life and is easy to perform. Note that there are differences in staining times depending on whether the specimen is fixed in Schaudinn or PVA fixative, as penetration is slower in the latter. 

Larval maturation studies, sometimes referred to as cultures, can be performed on fecal specimens applied to wet filter paper. Nematode larvae such as Strongyloides spp. or hookworm mature to the filariform stages in the culture container and migrate from feces into water, where they are detected microscopically. The procedure can be performed in a petri dish with a square of filter paper or in a large test tube with a strip of filter paper. 

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. 

Neutron activation analysis has low sensitivity for the detection of Mg. The best results were obtained in our hands by irradiating samples containing 200-300 yg natural magnesium (20-35 yg Mg) for one minute at a neutron flux of 10 cm sec followed by detection with a HP-6e detector. Since it is usually necessary to run activations in triplicate and to carry out additional analyses for total magnesium by an Independent method such as atomic absorption NAA is not suitable for specimens containing magnesium at low concentrations. It was found suitable for the analyses of fecal samples, marginal for urine and unsuitable for plasma (15,21). 

Oral sodium picosulfate and oral sodium phosphate have been compared for bowel preparation before elective colorectal surgery and colonoscopy in randomized studies in 256 patients (32). Oral sodium phosphate was superior to sodium picosulfate on surgical assessment of bowel preparation, fecal residue in the resected specimen, and endoscopic score. However, there was no significant difference with regard to abdominal pain, nausea, vomiting, embarrassment, fear, and fatigue between the two groups. 

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... 

Methods for porphyrin fractionation are complex and time consuming and not available in every laboratory. For this reason, simple qualitative screening tests are often used to exclude the majority of specimens that do not require further investigation from the few that justify fractionation of the individual porphyrins. Screening tests in which extracts of urine or feces are examined visually for typical red-pink fluorescence of porphyrins lack sensitivity and should not be used. Methods based on spectrophoto-metric scanning of acidified urine or fecal extracts for the presence of the Soret band are recommended and yield semiquantitative information. Quantitative fluorometric methods are also available. ... 

Johnston, S. P., Ballard, M. M., Beach, M. J., Causer, L., and Wilkins, P. P. (2003) Evaluation of three commercial assays for detection of Giardia and Cryptosporidium organisms in fecal specimens. J Clin Microbiol. 41, 623-626... 

The urine samples are usually treated with a mineral acid e.g. HCI, HNO3 or acetic acid for temporary preservation. However, for long term storage these human specimens need to be frozen, lyophilised or freeze-dried. Fecal samples should almost always be lyophil-ised or freeze dried before treatment. 

For urine analysis sample aliquots are diluted 1 1 with distilled water before application to the AAS stabilized temperature platform (Leung and Henderson, 1982). Fecal analysis require considerably more complicated preparation steps than serum or urine. The procedure developed in the author s laboratory (Brown et al., manuscript in preparation) is summarized as follows Frozen specimens are thawed and distilled water is added (1 mL per 2 g feces) and the sample is homogenized in a sealed container on a paint shaker. A 10 mL aliquot is ashed at 550°C in a muffle furnace, dissolved in dilute HNO3 snd analyzed by GF-AAS. 

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). 

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. 

Urine and fecal specimens can be shipped frozen on dry ice. Urines are then stored at 4°C, but for convenience, and aesthetic reasons, feces are sealed into 32 oz. plastic containers (Cole-Palmer, Chicago, IL) and kept frozen until processing. 

Data have been obtained concerning the stability of ampicillin in human stool specimens. Sixty-four to eighty-four percent of the ampicillin was recovered after 3-4 week storage of the stool-buffer blend in dry ice. A recovery cont control consisting of the sample stool-buffer blend dosed with a known amount of ampicillin was prepared for each sample. When a correction is made based on the recovered penicillin from the control, full recovery of ampicillin and stability through 3 weeks is obtained from the stool-buffer mixture . When ampicillin was incubated with the fecal flora of rats and tested for antibiotic activity, only 36.7% of the ampicillin activity was left after 4 hours . ... 

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