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| Example of Results |
| Test
Card Description and Instructions There are two windows on each test card to which a stool or gastric specimen can be applied. Attached to each card there is a liquid-containing pouch which is released by pulling the tab. After the tab is pulled, you will see a  control
on the edge of each test card which must turn blue indicating the test has
functioned correctly. A blue color in the window test areas is a positive
result. No blue in the test areas means no blood was detected. 1. Open the front cover of one Hemaprompt card and using the applicator spread a very thin smear of the specimen on one of the windows. When testing feces, from a different area of the stool, spread a second specimen thinly on the second window. Close the card cover.
2.
After closing the card cover turn to the back of the card. Grip with the
left thumb and finger at the point indicated and hold the foil tab with
the right thumb and finger. Alternatively lay the closed card face down
flat on a table and hold in place with your left thumb at the indicated
grip point. Slowly and steadily pull the foil tab all the way out to the
right and off. Wait one minute after pulling the tab before reading the
test result.
3. Check that the indicator
marked "control" has turned blue. If it has not turned blue the test card
is faulty and should be discarded. After one minute, inspect the indicated
window test areas. Any shade of blue no matter if it is faint or a small
speck in either one of the test areas is a positive reaction and indicates
that blood is present. Do not read after 3 minutes as the blue color may
fade. After noting the results, discard (do not flush) the card and applicator
safely. See Examples of Results page for colored illustrations of results
you might expect to see. |
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HemaPrompt fg is a
guaiac-based in-vitro slide method for the qualitative detection of occult
blood in feces and gastric aspirate or vomitus by medical professionals
only. For fecal testing, it is a useful aid in the diagnosis of a number
of gastro-intestinal disorders, and is recommended for use in 1) routine
physical examinations 2) routine hospital testing 3) screening for colorectal
cancer or gastro-intestinal bleeding from any other source. For the testing
of gastric contents it is used for the early detection of occult blood
in conditions such as gastric trauma, gastric or duodenal ulceration,
gastric cancer, esophageal varices, situations of likely exogenous or
endogenous gastritis, leukemia, and hereditary telangiectasia. These conditions
may be encountered in the emergency room, recovery room or intensive care. |
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Summary and Explanation Summary and Explanation Principle Reagents and Materials Supplied Storage and Stability Warning and Precautions Patient Preparation Specimen Collection Interpretation of Results Limitations of Test Expected Results Performance Characteristics Home The guaiac-peroxidase reaction, initially described by Van Deen [1], when adapted to the slide format, has been a widely used method for the detection of fecal occult blood, which is a sign of many gastro-intestinal disorders, and signals the necessity of follow-up by other diagnostic methods. Guaiac slide tests overcome the instability of guaiac solution and the hypersensitivity of benzidine and ortho-tolidine. The same reaction has also been used for the detection of occult blood in gastric contents ( when suitably buffered as with HemaPrompt fg ) indicative of a number of disorders such as gastritis, ulcer, or cancer. Blood is normally absent in the stomach, and when present secondary to benign ulcer will disappear with adequate therapy, but if persistent during medical treatment, malignancy is to be suspected [19]. HemaPrompt fg provides a method of testing for the presence of occult blood in which a thin smear of feces or gastric contents to be tested is applied to the guaiac paper window. The convenience of HemaPrompt fg is that the buffered developing solution is contained on each individual test card in a pre-measured quantity, and is applied automatically to the guaiac paper by pulling the tab on the card and unaffected by pH in the range of 1.0 - 8.0. The application of developer solution from a separate dispenser bottle is thus avoided. In addition, a monitor printed on the guaiac paper indicate if the chemicals are functioning correctly. HemaPrompt fg results cannot be considered conclusive evidence of the presence or absence of GI bleeding or pathology. False positive/negative reactions are known to be caused by a person's particular diet or medications (see Patient Preparation below). The test is intended as a preliminary indicator and not as a replacement for other diagnostic procedures such as gastroscopy, sigmoidoscopy, barium enema, and x-ray studies. ^ top of page |
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Principle The use of guaiac as a test for the presence of blood is based on the oxidation of phenolic compounds present in guaiac to quinones, resulting in the production of a blue color [2]. If blood is present, the heme portion of the hemoglobin (Hgb) molecule can function in a pseudoenzymatic manner, catalyzing the release of oxygen from hydrogen peroxide which in turn causes the oxidation of guaiac. HemaPrompt fg is a version of the laboratory guaiac slide test for fecal or gastric occult blood, and is composed of guaiac-impregnated paper mounted on a cardboard frame which permits sample applications to one side with development and interpretation from the reverse side. Feces or gastric contents containing occult blood contacts the guaiac impregnated paper and a pseudoperoxidase reaction occurs when developing solution is brought into contact with the guaiac paper, by pulling the tab. The test paper will turn blue in less than 60 seconds in the presence of more than 2mg hemoglobin/ gram of feces, and will gradually fade in 5 - 15 minutes. It will also turn blue in the presence of more than 0.01 mg hemoglobin/ ml of gastric fluid in less than 60 seconds, (see Performance Characteristics below). Monitors on the guaiac slide indicate if the chemicals are functioning correctly ^ top of page |
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Reagents and Materials Supplied Guaiac impregnated paper and developing solution are both mounted on each slide, as is a control monitor. The developing solution of 60-70% denatured ethyl alcohol and approximately 6% hydrogen peroxide diluted approximately 20% by a buffering mixture is contained within a developing pad and is exposed after pulling the tab. The positive monitor contains a hematoid equivalent to a minimum of 2.0 mg Hb per gram feces. The fecal specimen is usually applied directly by the gloved finger, from toilet paper or by applicator (as supplied). Gastric specimens can be applied directly from the naso-gastric tube or by obtaining a specimen from the container of gastric juice by means of the applicator supplied or by a clean cotton tipped swab ( not supplied). There are 50 slides with applicators in each box (Catalogue Number HPfg). Important Note Current U.S. Postal Regulations prohibit mailing completed test slides in standard envelopes. ^ top of page |
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Storage and Stability Each slide is equipped with controls to monitor the effectiveness of the chemicals and hence the test itself. The positive control must turn blue. Failure of the control to produce the appropriate color reaction is indicative of product deterioration and the test results are invalid. HemaPrompt slides should be stored at room temperature(15-30C) and should be protected from heat, sunlight, fluorescent light, U-V radiation, humidity, volatile chemicals and gases. Do not refrigerate or freeze. They are stable until the expiration date indicated on each slide, after which time the slide should not be used. ^ top of page |
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Warning and Precautions Reagents and Materials Supplied Storage and Stability Warning and Precautions Patient Preparation Specimen Collection Interpretation of Results Limitations of Test Expected Results Performance Characteristics Home HemaPrompt is intended for in-vitro diagnostic use only. Skin or eye contact with the developing pad which is exposed after pulling the tab, should be avoided; flush the affected area with water should contact occur. Ingestion may be fatal or cause blindness. Keep away from heat, sparks or open flame. ^ top of page |
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Patient Preparations i) Fecal Occult Blood. In the acute situation no particular preparation will be possible, but for screening purposes a special diet as described below is recommended to decrease the possibility of false positive results. On the other hand, dispensing with such a diet for initial screening purpose may increase patient compliance but a positive result under these circumstances would indicate the need to repeat the test in which a special diet two days prior to and during the three day test period is followed. This diet should EXCLUDE red and rare meats, horseradish, raw fruits and vegetables like broccoli, cauliflower, red radish, cantaloupe, parsnips and turnips, or other high peroxidase containing vegetables, which can cause false positive results. An acceptable diet could include cooked fruit and vegetables such as spinach and corn as well as lettuce, prunes, grapes, and apples. Cereal, and well cooked fish and fowl are also acceptable. If any of the recommended foods are known to cause discomfort, the patient should consult his or her physician. Because gastro-intestinal lesions may bleed intermittently and blood in feces is not distributed uniformly, all patients who test positive regardless of diet should be followed up with additional diagnostic procedures. Certain medications such as aspirin,[3] indomethacin, phenylbutazone, reserpine, corticosteroids and nonsteroidal anti-inflammatory drugs can cause gastro-intestinal bleeding and thus give positive reactions; dosages of greater than 250mg. of Vitamin C per day have been shown to cause false negative results[4], while iron containing compounds have been mentioned as a cause of false positive reactions[5].On the advice of the physician, these medications might be temporarily discontinued for 7 days prior to and during the test period. ii) Gastric Occult Blood Elective collection of gastric juice is rarely conducted. False positive and false negative reactions can be caused by medications and foods such as mentioned above. In addition, using a guaiac based test with an unbuffered developer, certain histamine (H2) antagonists such as cimetidine (Tagamet) have been shown to cause false positive reactions [16] as with iron, and false negative reactions can result from low pH, but because of the buffering of the developer used in HemaPrompt, interfering reactions by recommended dosage of ranitidine (300mg), ferrous sulfate (300mg),cimetidine (300mg) or antacids (Mylanta10-20 ml) have not been observed [21]. ^ top of page |
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Specimen Collection Feces can be obtained by direct rectal exam, but for screening purposes stool samples should not be collected if the patient is experiencing menstrual bleeding, constipation bleeding, bleeding hemorrhoids when rectal suppositories or medication is being used or if there are cuts on the hand. It is recommended that smears be collected from two different areas of each stool from three consecutive bowel movements as closely spaced in time as possible,[6][7], or by the physician following a rectal exam. Using toilet paper, a specimen is taken from stool smeared on the bowl and above the toilet water level, from the toilet paper used following defecation, or from a specimen caught in a clean cup. Application to the slide may be performed from the gloved finger (as after a rectal exam), applicator, or by use of the toilet paper described above. It is important that the stool specimen is applied as a thin smear to each of the slide windows and that no more than 4 days should elapse between preparation and testing, with patients being instructed to return all slides to the physician as soon as possible. Rehydration of the specimen is not necessary nor recommended. Gastric Contents obtained from the naso-gastric tube or vomitus can be applied directly from the naso-gastric tube or by means of a cotton tipped swab. In each case only a thin smear of material should be applied to the test area on the slide and developed (by pulling the tab as described on each slide) immediately and read within one minute. The specimen as applied to the slide or by itself may be stored up to 24 hours at room temperatures or up to 5 days at 30C before developing. Occasionally gastric samples applied to the slide may appear green in which circumstances only the formation of blue can be regarded as positive Patient specimens and all materials that come in contact with them, should be handled as potentially infectious and disposed of with proper precaution. Do not allow contact with skin or mucous membranes. ^ top of page |
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Interpretation of Results Results Limitations of Test Expected Results Performance Characteristics Home For both Gastric and Fecal samples, after pulling the tab out to its limit, results are to be read from the reverse side of the card and through the clear plastic window. ANY trace of blue coloration is to be regarded as a positive for occult blood. An absence of blue indicates no detectable occult blood. These results should be read at room temperature (16-32C) after 30 seconds and before 1 minute of pulling the tab. Within this time period, the proper functioning of the reagents is indicated by the positive monitor turning blue; should the monitor reaction be different, the test result is invalid. Contact Aerscher at 800 474 4072 for assistance if an invalid test result occurs. Color blind persons should not interpret the results. Neither the intensity nor the shade of blue from the positive Control Monitor should be used as a reference for the appearance of positive test results. ^ top of page |
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Limitations of Test Gastro-intestinal cancers, adenomas and ulcerations do not always bleed. Results cannot be considered conclusive evidence of the presence or absence of GI bleeding or pathology, and false positive or negative reactions are known to occur under certain circumstances such as a person's diet, medication, or traumatic use of a nasogastric tube (see Patient Preparation above). The test is not intended as a replacement for other diagnostic procedures and further testing and examination by the physician such as esophago-gastroscopy, sigmoidoscopy, barium enema, and imaging studies needs to be performed to determine the exact cause and source of the occult blood. ^ top of page |
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Expected Results The use of guaiac impregnated paper for the detection of fecal occult blood has been extensively studied and these clinical studies indicate that guaiac impregnated slide tests yield a positive result 3-5% of the time in screening programs and the percent of false positive results lies in the range of 1-2% of persons on a controlled diet [8][9][10] , with the normal daily fecal blood loss in an adult lying in the range of 1-2 mls. of blood per 100 gram of stool [11]. Sensitivity(% of subjects with the condition being sought who test positive) is difficult to estimate, but in series of patients with known colorectal cancer, 50-87% have been reported to yield positive reactions[12][13][14] Estimates of positive reactions with adenomatous bleeding have varied widely, and appear dependant to a degree on the size of polyp, with polyps less than 2 cms yielding less than 5% positive reactions.[15]. The significance of gastric occult blood has been less extensively studied than fecal occult blood. One study [17] of 153 gastric aspirates from 50 intubated healthy adults indicated all aspirates with more than 50 micrograms of hemoglobin/ ml were positive. There was an apparent overall false positive rate of 25.5% in this study of normal individuals, but even using less than 25 micrograms of hemoglobin / ml. as the test cut-off 11.8% showed a positive reaction. Another study [18] using 4 intubated healthy adults where blood was added to gastric juice, showed only positive reactions when 200 or more micrograms of hemoglobin / ml. was present in gastric juice at less than pH3. The false positive rate will obviously be affected by the test used and the method of collection - use of a large naso-gastric tube is often seen to cause bleeding initially. In practically all clinical situations where gastric juice is obtained, some degree of bleeding might be expected. The false negative rate has not been established . In anorther study [20] involving gastric samples from 10 patients and 10 healthy volunteers gastric samples with HemaPromt, it was found that all samples with blood added to produce concentrations of 0.1 mgHb/ml or greater reacted positively in pH ranges of 1 to 8. ^ top of page |
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Performance Characteristics Feces: Hemoglobin was diluted to the following concentrations: 1,2,4 and 6 mg/ml, equivalent to 0.1, 0.2, 0.4 and 0. 6 grams hemoglobin per 100 grams of stool or approximately 1,2,4 and 6 mls. of blood per 100 grams of stool. These dilutions were used to test the sensitivity of HemaPrompt fg as well as to compare the reactions of one other commercially available guaiac slide tests concurrently with HemaPrompt. In testing with blood-spiked normal stool, HemaPrompt fg reacted positively at hemoglobin concentrations of 2mg/ml or greater, in less than 60 seconds, with no reactions below this concentration. Hydrating stool (unless dried by age) by adding distilled water may produce reactions below this level by eluting blood out or the sample and onto the test paper and false positive reactions are possible. Gastric Juice: The reactions of HemaPrompt fg to the presence of blood in gastric juice were compared to one other commercial gastric occult blood test, and tested in the following manner. Twenty batches of gastric juice obtained by aspiration from different individuals, ten with gastric pathology and ten from healthy volunteers. Each sample was divided into 5 further samples and the pH in each adjusted to produce samples at pH 1.0, 2.5, 4.0, 6.0 and 8.0 respectively (simulating the varying pHs likely to be encountered in gastric juices ). Each of these samples had blood added so as to provide hemoglobin levels of 0.005, 0.01, 0.05, 0.1, 0.2, 0.5, and 1 mg hemoglobin / ml Gastric juice - i.e. a total of 35 samples were available for testing, reproducibility, and comparison to another commercially available product. These test results showed excellent precision and reproducibility at all pH and blood levels. They were performed 4 times the same day, and on three subsequent days on the same samples. Levels of hemoglobin above 0.02 mg/ml gastric juice always produced a reaction in less than 60 seconds and were negative below this level. Similar results were seen with to another commercially available test designed for gastric occult blood and it was found that this product reacted in a like manner. Furthermore, concentrations of ranitidine, cimetidine, ferrous gluconate, and an antacid (Mylanta) to be expected in the stomach after a maximum recommended dose did not alter the results. All monitors reacted in the expected manner (+ve turned blue ). Exposing the guaiac paper to UV light for ten minutes inactivated the expected reaction. It was concluded that with stool, HemaPrompt fg reacted positively and definitely to all hemoglobin levels above 2mg/G of stool at which level another commercially available guaiac slide test, when used in its indicated manner, reacted comparatively and similarly. It was further concluded that with gastric juice, HemaPrompt fg reacted positively and reliably to hemoglobin added to levels above 100mcg / ml of gastric juice. ^ top of page |
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WSLH
Comparison Study An independent comparison study was conducted by the WSLH Proficiency Testing Program. HemaPrompt FG and Gastroccult (20 slides of each product) were used to compare sensitivity to Hemoglobin in synthetic gastric juice (manufactured by WSLH Proficiency Testing ) over a range of Hgb concentrations (500ug/ml minimum) and pH range 1 - 7. No significant differences were found between the two products and each was found equally suitable for the detection of Hemoglobin in gastric juice in the pH range of 1 to 7. ( September 2003) ^ top of page |
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| © 2008 Aerscher Diagnostics. All rights reserved. | Aerscher Diagnostics / 819 B High Street / Chestertown, MD 21620 / 800.474.4072 / aers@dmv.com |
