Evaluation of radiochromium blood loss studies in unexplained iron-deficiency anaemia

Carbonic anhydorase isoenzyme I (CA-I) concentration in feces and urine as a temporary marker of occult blood in beagle dogs

This study was undertaken to investigate whether the concentration of carbonic anhydorase isoenzyme I (CA-I) in canine feces and urine is useful as a temporary marker of occult blood. Concentrations of CA-I were measured by enzyme-linked immunosorbent assay (ELISA). Fecal CA-I concentrations in 113 healthy beagle dogs (50 male and 63 female) of various ages ranged from 4.3 to 16.7 ng/g feces (mean; 7.0 +/- 2.9 ng/g feces). One milliliter of blood from 3 healthy beagle dogs was found to contain 1,047, 1,062 and 1,150 microg CA-I. The fecal CA-I concentrations of dogs receiving intragastric infusions of autologous blood (10 ml) were very low. However, the fecal CA-I concentrations of dogs receiving infusion of autologous blood (5 ml) into the ascending colon were very high. Detection of fecal CA-I would be useful for identifying dogs with hemorrhaging of the large intestine. Of 55 urinary samples collected from healthy beagle dogs by catheter, chemical tests for occult blood were negative in 44, but CA-I concentrations ranged from 1.8 to 12.6 ng/ml (mean; 6.9 +/- 5.4 ng/ml) by ELISA. The CA-I concentrations of the other 11 samples, which tested positive for occult blood on chemical testing, ranged from 41.2 to 525.0 ng/ml by ELISA. Although CA-I is not a specific marker of erythrocytes, CA-I may be used to detect occult blood in canine feces and urine until a specific immunological test kit using antibody for Hb is developed.

Silent angiodysplasia and occult haemobilia as rare but treatable causes of refractory iron deficiency--two case reports

Once menorrhagia has been excluded in females then, in both sexes, the gastrointestinal tract remains the commonest site for haemorrhage. This may be of surprisingly large volume but intermittent and therefore not universally demonstrated on stool testing. However, if loss is persistent it may nevertheless culminate in absolute iron deficiency and thus, even when occult blood is not present on repeated examinations, quantitation using chromium labelled red cells becomes invaluable. In this situation, endoscopy or contrast radiology of the small and large bowel may fail to reveal any lesion even when these procedures are repeated or used in combination. Modifications by direct inspection or camera study may be helpful in improving diagnostic accuracy. It is nevertheless practical, as illustrated by these two cases, to more widely recognise the value of radionuclide scanning methods. In one this was due to unsuspected haemobilia and the second to major duodenal vascular malformation although it could be reasonably argued that initial recourse to angiography might have demonstrated this. The principle is that when precisely defined anatomically surgery can be elective and limited as a result of careful proactive planning and operations likely to have a high initial rate of success. The role of nuclear medicine in the investigative algorithm of such patient is re-emphasised. Thus, in any individual with unexplained but proven absolute iron deficiency failure to reveal the cause by first screening with gastroscopy and colonoscopy or barium studies including the small bowel should not automatically be repeated. Rather, the blood loss needs to be documented and, if possible, subsequent evaluation moved to advancement or push enteroscopy, capsule endoscopy or the more invasive angiography only once quantity a pattern of bleeding are defined by radioisoptic imaging.

Occult gastrointestinal bleeding

Occult gastrointestinal bleeding commonly manifests as iron deficiency anemia or fecal occult blood. Iron deficiency anemia results from chronic occult gastrointestinal bleeding. Evaluation of asymptomatic patients who have iron deficiency anemia or fecal occult blood usually should begin with investigation of the colon. Colonoscopy is preferred, but flexible sigmoidoscopy plus air contrast barium enema, or computed tomographic colonography may be acceptable in certain circumstances. If evaluation of the colon does not reveal a bleeding site, evaluation of the upper gastrointestinal tract is mandatory in patients who have iron deficiency anemia, and this should be considered in those who have fecal occult blood. In patients who have gastrointestinal symptoms, evaluation of the portion of the gastrointestinal tract from which the symptoms is derived should be pursued initially. The role of small intestinal investigation is controversial, and this probably should be reserved for patients who have iron deficiency anemia and persistent gastrointestinal symptoms or those who fail to respond to appropriate therapy. Celiac sprue should be considered as a potential cause of iron deficiency anemia in all patients. The treatment and prognosis of patients who have iron deficiency anemia or fecal occult blood depends on the gastrointestinal tract abnormality(ies) identified. Those without identifiable bleeding sites generally respond to conservative management and have a favorable prognosis. On the other hand, the outlook is poorer for patients with refractory occult blood loss or those who have vascular ectasias. Both groups of patients are clinically challenging and require a focused and experienced team approach to diagnosis and therapy.

Immunological determination of faecal haemoglobin concentrations in dogs

Faecal haemoglobin (Hb) concentrations in apparently healthy experimental Beagle dogs and in dogs of various breeds kept in private households or at breeders were measured by reversed passive latex agglutination (RPLA) and enzyme-linked immunosorbent assay (ELISA) in an effort to define the physiological concentrations of faecal Hb in the dog. In 88% (53) of 60 experimental Beagle dogs (30 males and 30 females), the RPLA titres were 1:2 and 1:8 and the faecal Hb concentrations ranged from 40.0 to 431.5 (mean 184.1 +/- 92.6) micrograms/g faeces by ELISA. No significant difference was found in Hb levels or RPLA titres between males and females. Seven dogs (12%) had significantly greater RPLA titres and Hb concentrations by ELISA than the remaining dogs. In 84% (45) of the 53 dogs kept in private households or at breeders, the RPLA titres were < 1:1 to 1:8 and the faecal Hb concentrations ranged from 7.1 to 456.7 (mean 137.5 +/- 128.7) micrograms/g faeces in ELISA. Eight of these dogs (15.1% of 53 dogs) had significantly greater RPLA titres and Hb concentrations by ELISA than the remaining dogs. There were no significant differences between the Beagles and dogs kept in private households or at breeders. In conclusion, in 98 (86.7% of 113) dogs the physiological concentrations of RPLA titres were < 1:1 to 1:8 and the faecal Hb concentrations were 143.5-185.1 micrograms/g (95% confidence level). Approximately 13.3% of apparently healthy dogs had higher faecal Hb concentrations, suggesting the presence of subclinical haemorrhages. Four dogs suffering from colorectal cancer also had high faecal Hb concentrations.

Measurement of occult upper gastrointestinal tract blood loss: a direct comparison of radiochromium and haem-porphyrin assay techniques

Faecal haem-porphyrin assay by the HemoQuant method has many practical advantages over the well-validated, radiochromium (51Cr-tagged red cell) method for measuring gastrointestinal blood loss. Because haem may be absorbed but the chronic ion is not, the two measures were directly compared in low-grade bleeding from the proximal gastrointestinal tract. Blood loss was measured by both methods simultaneously in 40 patients with osteoarthritis before and during medication with aspirin preparations. Mean (geometric) daily blood loss before aspirin usage measured 0.60 mL radiochromium (range 0.13-1.62) and 0.47 mL (0.14-1.40) by HemoQuant (P = 0.042). On aspirin, bleeding rose to 1.57 mL/day (0.43-4.85) by radiochromium and to 0.72 mL/day (0.23-3.0) by HemoQuant (P < 0.0001). The two measures correlated well, r = 0.847 (P << 0.0001), but the regression coefficient was 0.417, reflecting the lower estimates of bleeding by HemoQuant. In four normal subjects who ingested 51Cr-labelled red cells (26-41 mL) over 3 days, recovery of 51Cr was complete (103 +/- 2%, +/- s.e.), but recovery of haem-porphyrins was only 63 +/- 13% (P = 0.01), presumably because of absorption of haem. Although faecal haem-porphyrin assay is of considerable clinical utility, it is a quantitative index rather than an absolute measure when low amounts of bleeding originate from the proximal gastrointestinal tract.

Haem in the gut. Part II. Faecal excretion of haem and haem-derived porphyrins and their detection

Only a fraction of haem (ferroprotoporphyrin) finding its way into the gut lumen is absorbed; the major portion enters the colon. There, unabsorbed haem, together with any haem of haemoproteins shed directly into the colonic lumen as haemoglobin or other haemoproteins, are converted by bacteria to a range of haem-derived porphyrins (HDP) lacking iron. This conversion is a slow and incomplete process and the amount converted in this way depends on colonic transit rate, site of bleeding and amount of luminal haem. As a consequence, faeces contain variable proportions of haem and HDP. The guaiac and tetramethylbenzidine tests give a qualitative index of faecal blood; they depend on the pseudoperoxidase activity of intact haem and cannot detect HDP. These tests perform better for large bowel bleeding than for more proximal bleeding. The fluorimetric HemoQuant assay quantitates both haem and HDP; it performs well for both proximal and distal bleeding. Neither type of test can allow for intestinal absorption of haem or HDP. Quantitation of gastrointestinal bleeding derived from measurement of faecally excreted haem and HDP is, therefore, likely to underestimate haem delivered into the gut lumen. In a given clinical situation, the choice of a haem-dependent occult blood test must take into account the possibility of colonic conversion of haem to HDP and the possible value of quantitation as opposed to qualitative detection.

An immunologic test for fecal occult blood by counter immunoelectrophoresis. Higher sensitivity and higher positive reactions in colorectal cancer than single radial immunodiffusion and hemoccult test

A new immunologic fecal occult blood test has been developed employing counter immunoelectrophoresis (CIEP) with anti-human hemoglobin Ao antiserum (anti-HbAo). Minimum detectable hemoglobin in hemolysate was 7, 9, and 7 micrograms/ml by CIEP, single radial immunodiffusion (SRID), and Hemoccult test (SmithKline Beckman), respectively. The values in stool were 0.5, 1.0, 3.0 mg hemoglobin/g stool in the same order. CIEP was more sensitive than SRID in detecting hemoglobin both in hemolysate and in feces. Of 38 stools from the patients with colorectal cancer, 29 (76%) gave positive tests in CIEP, whereas 22 (58%) (P less than 0.005), and 18 (47%) (P less than 0.05) gave positive tests in SRID and Hemoccult test, respectively. In every stage and at every site of cancer, CIEP showed the highest positive tests. CIEP did not give any false-positive reaction in specimens from 20 patients without gastrointestinal lesion or from 34 asymptomatic healthy controls without diet restriction, whereas Hemoccult test gave one and three positive reactions in these groups. These results clearly indicate that CIEP is specific and more sensitive to human hemoglobin than any other previous methods. CIEP is expected to have a potential for mass screening of colorectal cancer.

Five guaiac-based tests for occult blood in faeces compared in vitro and in vivo

Five guaiac-based faecal occult blood tests (Fecatest, Fecatwin Sensitive, Fecatwin, Haemoccult, Hemafecia) were compared in vitro and in vivo and the effect of time between sample application and development of the colour reaction was studied. In both type of experiments the sensitivity of Fecatest, Fecatwin Sensitive and Fecatwin was higher when the colour reaction was developed at 24-72 h than at 2 h after application of the sample but for Haemoccult and Hemafecia the sensitivity in in vivo experiments was constant or tended to decrease with time. In upper gastrointestinal bleeding false negative test results were obtained for Fecatest, Fecatwin Sensitive, Fecatwin, Haemoccult and Hemafecia in 21, 23, 38, 43 and 43%, respectively. In colorectal bleeding the corresponding percentages were 10, 10, 35, 35 and 35. Using the 51Cr-erythrocyte method, quantitative estimation of intestinal bleeding was performed in 20 patients with verified colorectal cancer and in 11 control patients. When the patient was bleeding from left hemicolon 29% of the Fecatwin, Haemoccult and Hemafecia test results were negative, 10% were negative for Fecatest and 14% for Fecatwin Sensitive. In patients with tumours in right hemicolon Fecatest and Fecatwin Sensitive were positive in all samples, whereas the other tests were negative in 10%. Experiments revealed that the proportion of false positives due to dietary factors correlated with the sensitivity of the tests.