ACADEMIA AND CLINIC
`
`A Stool Collection Device: The First Step in Occult Blood Testing
`
`DAVID A. AHLQUIST, M.D.; SAMUEL SCHWARTZ, M.D.; JAMES ISAACSON, B.S.; and MARK
`ELLEFSON, B.S.; Rochester and Minneapolis, Minnesota
`
`Despite widespread fecal blood testing, the technique of
`gathering stool for sampling has remained uncontrolled.
`We sought to describe how patients have contended with
`this awkward step, to study artifact caused by toilet water,
`and to construct a collection device that prevents
`sampling problems. A survey of 2 5 0 patients showed that
`most ( 5 6 % ) had retrieved stools from the toilet basin,
`1 7 % used a pan or other household receptacle, 1 0 %
`used newspaper or tissue paper, and 1 7 % had been
`unable or unwilling. Sampling stool from the toilet basin
`introduces error because 4 % to 7 5 % of blood leaches
`from the fecal surface into surrounding water after only 4
`to 12 minutes, and many toilet sanitizers cause false-
`positive guaiac reactions. We describe an inexpensive,
`disposable stool collector; outpatient compliance has
`been 9 7 % using this device. To avoid biochemical artifact
`and facilitate stool sampling, we advocate that a collection
`device be incorporated into the occult blood testing
`process.
`[MeSH terms: guaiac; occult blood; patient compliance.
`Other indexing terms: fecal blood testing; HemoQuant; stool
`collection; stool collection device]
`
`THE AMERICAN Cancer Society currently recommends
`annual surveillance for colorectal neoplasia by fecal
`blood testing in persons aged 50 or older. However, the
`testing process remains unsystematized. The many tests
`available differ in biochemical and clinical performance
`(1-5). Numerous dietary constituents (6-8), medications
`(5, 9-12), storage of assay materials (13), delays in speci(cid:173)
`men handling (5, 14), and fecal hydration (5, 15, 16)
`alter the reactivity of commonly used tests. Proper inter(cid:173)
`pretation of fecal blood test results mandates careful con(cid:173)
`trol of each step of the testing process.
`The first step in the screening process, procurement of
`stool for testing, has been largely ignored in commercial
`test kit instructions and in many reported screening trials
`(17-27). Patients are usually directed to smear an aliquot
`of stool onto a test pad using a 3-inch wooden stick pro(cid:173)
`vided in the kit—an unwieldy task for some, especially if
`the stool has sunk. How the stool is gathered and sam(cid:173)
`pled has surprisingly been left to patients' ingenuity.
`Sampling a stool from within the toilet basin may not
`only be technically difficult, but create potential measure(cid:173)
`ment artifact due to disintegration of the specimen, loss
`of blood from stools into the surrounding water, or con(cid:173)
`tamination from commercial disinfectants and other toi(cid:173)
`let water additives. Regardless of which assay is used,
`
`• From the Departments of Internal Medicine and Medical Engineering, Mayo
`Clinic, Rochester; and Minneapolis Medical Research Foundation, Minneapolis,
`Minnesota.
`
`Annals of Internal Medicine. 1988;108:609-612.
`
`variability in the technique of stool collection may con(cid:173)
`found results.
`This report presents the range of approaches patients
`have taken to recover their stools for sampling; examines
`potential quantitative and qualitative measurement errors
`caused by sampling stools from toilet bowl water; and
`describes a device designed to prevent collection-related
`problems in fecal occult blood testing.
`
`Materials and Methods
`A brief questionnaire was distributed to adult Mayo Clinic
`outpatients to explore the range of approaches patients have
`used to collect stools for occult blood testing. To encourage
`candid responses neither patient identification nor demographic
`information was requested. About 80% of patients returned the
`questionnaire. Patients were asked to detail how they had con(cid:173)
`tended with previous stool collections for occult blood testing.
`Because a stool collection device has been used at the Mayo
`Clinic for more than 2 years, only questionnaires from patients
`who had had occult blood testing outside of the institution were
`used; thus questionnaires from 250 respondents were consecu(cid:173)
`tively evaluated. The questionnaire was reviewed and approved
`by our Institutional Review Board.
`The HemoQuant assay (Minneapolis Medical Research
`Foundation, Minneapolis, Minnesota) was used to quantify the
`extent of hemoglobin transfer from stools to toilet water (28).
`Stools from healthy volunteers were thoroughly blended with
`blood and different amounts of water to produce test specimens
`with variable consistency and moderately elevated hemoglobin
`concentrations (range, 2.1 to 6.4 g/L). Corresponding to the
`superficial layer of stool, which is the portion most likely to be
`sampled by patients, thin specimen slabs of 3 X 10 X 10 mm
`or 6 X 10X 10 mm were prepared. Slabs were placed on a
`fiber glass mesh and immersed in a beaker of tap water without
`agitation. After time intervals of 4 to 12 minutes, fecal slabs
`were removed, and separate assay of the slabs and of their water
`baths were done. Results are reported as percent of initial fecal
`hemoglobin lost from the assayed stool or recovered from the
`water bath. Aliquots of all fecal specimens were weighed before
`and after desication to determine their percent dry weight.
`The effects of several time-release toilet bowl sanitizers on
`guaiac pad test reactivity were evaluated. Several commonly
`used brands were selected that are placed into the holding tanks
`and advertised to last from 1 to 4 months. Four brands generat(cid:173)
`ed chlorine (Tank 'n Bowl, Twin Oak Products, Piano, Illinois;
`2000 Flushes, Kleenco, Jersey City, New Jersey; Depend-O
`Crystal Clear, Boyle-Midway, New York, New York; and Bul(cid:173)
`ly, French Household Products, Rochester, New York) and
`two did not (Vanish Drop-ins, Drackett Products, Cincinnati,
`Ohio; and Bloo, Kiwi Brands, Douglassville, Pennsylvania).
`Dispensers were placed in 2-liter tanks of tap water. At 30 min(cid:173)
`utes and at 5 hours tanks were gently stirred and sampled.
`Solutions were placed as a single drop on each window of the
`guaiac pad tests Hemoccult (Smith-Kline Diagnostics, Sunny(cid:173)
`vale, California) and Seracult (Propper Manufacturing, Long
`
`© 1 9 8 8 American College of Physicians
`
`6 0 9
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`Table 1 . Effect of Time-Release Toilet Bowl Sanitizers on Guaiac
`Pad Test Reactivity*
`
`Toilet Bowl
`Sanitizer
`
`Incubation Time of Dispenser
`in 2-Litre Water Tank
`Hemoccult/Seracult
`Hemoccult/Seracult
`
`+ +/+ +
`+ +/+ +
`
`30 minutes
`Chlorine-generating brands
`Tank'n
`Bowl
`2000
`Flushes
`Depend-O
`Crystal
`+ +/+ +
`Clear
`+ +/+ +
`Bully
`Nonchlorine-generating brands
`Vanish
`Drop-
`insf
`Bloof
`
`( - / - )
`( - / - )
`
`5 hours
`
`+ + +/+ + +
`+ + +/+ + +
`
`+ + +/+ + +
`+ + +/+ + +
`
`( - / - )
`( - / - )
`
`* A single drop of each test solution was added to guaiac pad windows.
`t Although they do not cause a positive guaiac reaction, these products contain
`a blue dye that colors the tank water and stains the guaiac test pad windows blue.
`
`Island City, New York) and tested immediately with addition
`of the developer.
`The purpose of a collection device for occult blood testing is
`to conveniently, inoffensively, and reliably mobilize the stool for
`patient sampling before it mixes with toilet water. Because stool
`blood testing is advocated for a large segment of the general
`population, such a device must be cheap, easy to mail, use,
`dispose of, and mass produce. The collection device we describe
`was developed to satisfy these criteria.
`
`Results
`Patient approaches to stool collection varied, but could
`be grouped into four general categories. Most (56%)
`sampled their stools from within the toilet bowl water
`after retrieving the specimens using various techniques,
`including the short wooden stick provided in the test kit,
`long-handled
`ladle, rubber glove, or bare hand with
`rolled-up sleeve. Some (17%) caught their stool in a
`make-shift receptacle, such as a kitchen pan, bowl, or
`coffee can. Others (10%) defecated onto newspaper, toi(cid:173)
`let tissue, or wax paper held in the hand or placed on the
`floor. Finally, several patients (17%) indicated that they
`had been unwilling or unable to collect their stool. One
`patient specified that the stools could not be sampled be(cid:173)
`cause after several attempts they were lost through the
`exit port at the bottom of the toilet basin.
`Loss of hemoglobin from the prepared fecal slabs into
`water baths varied greatly, ranging from 4% to 75% of
`initial concentrations. Leaching of blood into the sur(cid:173)
`rounding water bath progressed over time from all fecal
`slabs (Figure 1). Loss of hemoglobin was greater from
`thinner slabs and from slabs of softer consistency. Nearly
`half the blood from some softer stools had transferred
`into the water bath after 8 minutes.
`Water solutions sampled from the four tanks holding
`chlorine-generating toilet bowl sanitizers all tested posi(cid:173)
`tive with both Hemoccult and Seracult (Table 1). Reac(cid:173)
`tions were moderately positive from solutions sampled 30
`minutes after sanitizer placement and strongly positive
`
`from solutions sampled after 5 hours. Neither of the non(cid:173)
`chlorine-generating sanitizers reacted with the guaiac
`pads; however, both brands (Vanish Drop-ins and Bloo)
`contained a blue dye that colored the water and stained
`the test pad windows a mildly to moderately deep sky
`blue (Table 1).
`The collection device (Ability Building Center, Inc.,
`Rochester, Minnesota) consists of two components: a
`cardboard yoke support that is water-repellent on the
`dorsal surface and a flushable filter paper dish that is
`porous to fluid (Figure 2). The paper dish attaches to the
`support on four tabs punched out of the cardboard itself.
`As the device is lightweight and flat before its use, it can
`be carried inconspicuously or mailed in an envelope. To
`prepare the support for mounting, patients fold up the
`pleated side wings that serve to stabilize the yoke and set
`the dish at the appropriate distance beneath the toilet
`seat. The collection device is then taped onto the back
`half of the toilet seat (Figure 2 ) . Finally, the center of
`the paper dish is depressed to shape a bowl that will
`accommodate defecation. Once the stool is evacuated
`onto the dish, an unadulterated sample may be obtained
`and sent to the physician, hospital, or laboratory.
`To dispose of the stool, the patient simply lifts the pa(cid:173)
`per dish at each tab site and flushes both the dish and the
`stool. The cardboard support is detached and either dis(cid:173)
`carded into a wastebasket or saved for additional sam(cid:173)
`plings. If more than one stool test is requested, extra pa(cid:173)
`per dishes and sampling tubes or test pads are given to
`the patient to use with the same cardboard support.
`This stool collection device has been used routinely for
`nearly 2 years with HemoQuant testing of outpatient, in(cid:173)
`patient, and mail-in samples at the Mayo Clinic. More
`than 100 000 tests have been done after the device has
`been used, and no major technical problems have been
`
`incubation
`Figure 1 . Effect of stool consistency, thickness, and
`time on blood loss from stool into water bath. Fecal slabs of vari(cid:173)
`able
`consistency measuring
`3 x 10 x 10 m m
`(A)
`or
`6 x 10 x 10 mm (B) were placed in a nonagitated tap water bath
`for variable times. Loss of fecal hemoglobin was determined by the
`HemoQuant assay and expressed as percent of initial fecal hemo(cid:173)
`globin concentration. Each point represents the average of two to
`five fecal preparations.
`
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`April 1988
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`• Annals of Internal Medicine • Volume 108
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`• Number 4
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`reported to date. Sample return rates have been extreme(cid:173)
`ly high among this large private patient population; based
`on a 1-week period of observation, 915 HemoQuant tests
`were ordered and 887 samples were returned to the labo(cid:173)
`ratory for analysis. This 97% return rate reflects both
`high patient compliance and technical success in obtain(cid:173)
`ing the stool sample using a system that incorporates the
`collection device.
`
`Discussion
`Despite widespread promotion of fecal blood screen(cid:173)
`ing, there has been conspicuous patient reticence on the
`matter of stool collection. Failure to control this critical
`step in the screening process results in inescapable bio(cid:173)
`chemical artifact, an awkward task for patients, and pos(cid:173)
`sibly reduced compliance. To avoid these undesirable se(cid:173)
`quelae, we have developed an inexpensive stool collector
`that is easy to mail, use, discard, and mass produce and
`that has been successfully used in outpatient, inpatient,
`and mail-in settings.
`We were unable to find published data on patients'
`approaches to stool collection for occult blood testing.
`Recent recommendations on how to do fecal blood tests
`include no mention of techniques to mobilize the stool for
`sampling (29). Responses from the survey in this report
`document the resourceful extremes taken by patients to
`accomplish this unpleasant task, including defecating
`onto a newspaper placed on the floor, catching the stool
`in a frying pan, and manually retrieving the stool from
`the bottom of the toilet basin. However, most techniques
`involved sampling the specimen from within the toilet
`bowl water.
`Sampling the stool from the toilet basin introduces ma(cid:173)
`jor variability. The portion of fecal blood lost into the
`toilet water is unpredictable. Using HemoQuant, we
`found that nearly half the blood contained in the superfi(cid:173)
`cial 3-mm layer of some stools leaches into the surround(cid:173)
`ing water after only 8 minutes, whereas other stools more
`avidly retain blood. As fecal blood levels from patients
`with colorectal cancer are commonly in the lower elevat(cid:173)
`ed range (15, 16, 30-32), this degree of measurement
`distortion might easily lead to false-negative results and
`missed diagnoses.
`There are additional toilet water variables that may
`obscure guaiac pad test results. Common household dis(cid:173)
`infectants added to toilet holding tanks cause chemical
`false-positive reactions. False-positives may also occur if
`stools are sampled from toilet bowl water contaminated
`by blood from urine or menstruation (33). Other sub(cid:173)
`stances excreted in urine, such as ascorbic acid ( 9 ) and
`naturally occurring constituents (11), may inhibit the re(cid:173)
`action with guaiac or related leuco-dyes used for blood
`detection and cause false-negative results. Finally, vari(cid:173)
`able fecal hydration may alter the reactivity of guaiac
`pads (5, 15, 16).
`Studies analyzing compliance to stool testing ( 1 , 24,
`26, 34-37) have shown the influence of certain demo(cid:173)
`graphic and socioeconomic factors but have not elaborat(cid:173)
`ed on patient aversion to the ordeal of stool collection.
`One report has shown that personal objection to stool
`
`Figure 2 . Collection device for stool sampling. The device consists
`of two components: a cardboard yoke and a flushable, easily de(cid:173)
`tachable paper dish. Side-wings are folded up along pleat lines t o
`stabilize the yoke and to fix the paper dish at the appropriate dis(cid:173)
`tance beneath the toilet seat (A). Attachment position of stool col(cid:173)
`lection device. For serial stool testing, the yoke may be re-used with
`additional paper dishes before disposal (B).
`
`sampling was more common in nonvolunteers than in
`volunteers to a Hemoccult screening program ( 3 8 ) .
`Patient compliance has ranged from 19% to 85% in re(cid:173)
`ported screening trials, generally being higher after a
`physician visit (17-27, 34-36). Compliance to guaiac pad
`testing has been as low as 26% (39) and 30% (24) even
`in patients who have registered to participate in screen(cid:173)
`ing. Patient reluctance to labor through the unpleasant
`retrieval of stool may influence these low compliance
`rates. The present study does not specifically test the im(cid:173)
`pact of the stool collector on patient compliance. Howev(cid:173)
`er, in our somewhat unique outpatient practice at the
`Mayo Clinic, the return rate of fecal specimens for the
`HemoQuant test, which incorporates the collecting de(cid:173)
`vice, was 97%.
`To avoid biochemical error and to facilitate a cumber(cid:173)
`some and unpleasant chore, we advocate the use of a
`collection device as a prelude to stool sampling in the
`occult blood testing process.
`ACKNOWLEDGMENTS: The authors thank Susan Laging, Jan DeLue,
`Peter Adams, and Page Edmonson for their assistance.
`Grant support: in part by the Mayo Foundation and Minneapolis Medical
`Research Foundation.
`Presented in part at the annual meeting of the American Gastroenterolog(cid:173)
`ical Association, May 1987, in Chicago.
`
`• Requests for reprints should be addressed to David A. Ahlquist, M.D.;
`Division of Gastroenterology, Mayo Clinic, 200 S.W. First Street; Roches(cid:173)
`ter, MN 55905.
`
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