Biomedical subjects
Publications and source records attributed to L N Daae.
The chemical tests used to determine blood in faeces and urine have not been recommended for determining blood in gastric contents, since highly acidic samples may give false-negative reactions. Based on model studies this article states that, in most cases, ordinary chemical tests for faecal blood may also prove useful for determining blood in gastric materials.
We review the construction, handling, advantages and drawbacks of serum separator tubes. A study is reported, which demonstrates that serum potassium measurements are less reliable when gel-barrier sampling tubes are used incorrectly. We give guidelines for correct use of such equipment.
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In 40 healthy adult volunteers of both sexes blood samples were taken simultaneously from an antecubital vein in EDTA-Vacutainers and from a fingertip in EDTA-Microtainers. Haematological measurements were subsequently performed in an Ortho-ELT 800 WS analyzer. Significant differences were obtained between the two sets of samples. In accordance with current literature, the 'capillary' thrombocyte count was either identical to, or more frequently substantially lower than the corresponding venous count. On the contrary, the 'capillary' erythrocyte count and the haematocrit and haemoglobin values significantly exceeded those of venous blood, while the red cell indices MCV, MCH and MCHC were identical. The total leucocyte count was substantially elevated in 'capillary' blood compared with the corresponding venous samples. Moreover, the 'capillary' differential leucocyte counts showed elevations which directly reflected the various particles' size. Possible explanations of these findings are discussed.
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A total of 754 persons randomly selected from the age group 55-64 years were invited by letter to take part in a screening for hematuria, proteinuria and glucosuria. Each person was asked to provide one sample of morning urine and immediately mail it to the laboratory. A total of 413 persons (55%) responded. Two dipsticks: BM-Test-5L and a new single strip for hematuria determination preliminary named BM 33075 were used, both manufactured by Boehringer Mannheim GmbH. The test strips gave positive reaction for hematuria in 21 persons (5.1%), for proteinuria in 14 persons (3.4%), and for glucosuria in six persons (1.5%). All persons with positive tests were invited to follow-up investigations. In the hematuria group we found one person with a malignant disease, 13 with benign conditions and in seven persons we found no reason for the hematuria. Among those with proteinuria one person had a nephritis. Four persons with glucosuria knew about their diabetes mellitus. The cost of the screening was NOK 99 per participant.
In 67 patients referred for colonoscopy the faecal blood loss was determined by a 51Cr method and 7 chemical tests. For patients with negative colonoscopy (no. = 10), colorectal polyps (no. = 24), rectal cancer (no. = 8), or colonic cancer (no. = 12), the median 51Cr-determined faecal blood loss was 0.67, 0.74, 1.26, and 2.18 ml/24 h, respectively. For all chemical tests the results were highly influenced by the upper time limit for a positive reaction. Mixing of faecal specimens before testing proved unimportant. Fecatwin sensitive showed more positive tests in delayed compared with immediate analyses (p less than 0.01). Of cases of colorectal polyps, tetramethylbenzidine (TMB) tests including Hemo-Fec Test could detect half, the benzidine test 2 of 5. Fecatwin sensitive and Hemoccult II 1 of 4, and Fecatwin 1 of 24. Of cases of colorectal cancer, TMB tests, the benzidine test, Fecatwin sensitive, Hemoccult, and Fecatwin could detect about 85%, 85%, 85%, 80%, and 45%, respectively. All chemical tests detected faecal blood loss from colorectal lesions more easily than from gastric lesions.
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The inhibitory effect of ascorbic acid on commercial test strip reactions for haematuria is demonstrated in vitro. A new test strip containing iodate is shown to be insensitive to even high ascorbic acid concentrations in the same in vitro experiments.
The influence of ascorbic acid on commercial rapid diagnostic tests for glucosuria is demonstrated in vitro. Although much work has been done to stabilize the tests against such interference, and although manufacturers of tests trips declare their products now to be fairly stable against ascorbic acid 'at higher glucose levels', all the investigated commercial rapid diagnostic tests for glucose at the lower pathological range of glucosuria were substantially influenced by ascorbic acid at potentially physiological concentrations.
Bleeding times were determined in 25 healthy men using the Thrombolette bleeding time device. The median bleeding times prior to low and high doses of acetylsalicylic acid (ASA), 245 and 230 s, were not significantly different (P = 0.12). 2 h after randomized ingestion of 0.44 and 3.96 g ASA, the median bleeding times rose to 450 and 430 s, respectively. Both increased in bleeding time were significant (P less than 0.001), but the difference was not significant (P = 0.29). The maximum increase in bleeding time was estimated to occur 2.6 h after ingestion of a single low ASA dose, and 2.4 h after a single high dose. Following ingestion of 0.44 as well as 3.96 g ASA the bleeding time returned to basal levels within 5-6 d. Compared to the younger ones, volunteers with a higher age showed a tendency to have lower plasma salicylate levels as well as smaller increases in bleeding times following ASA ingestion.
Stools from volunteers participating in an acetylsalicylic acid (ASA) study were examined during periods with restrictive and liberal diets. With 51Cr-determined faecal blood less than 2 ml/100 g, the rates of positive benzidine and 3,3' ,5,5'-tetramethylbenzidine (TMB) tests were about 5% and 25% for periods with restrictive and liberal diets, respectively. Similarly, Fecatest showed 2% positive tests on a restrictive and 8% on a liberal diet, whereas Hemoccult II slide and BM-test-Hemafecia showed less than 5% positive tests on both diets. When ASA-induced blood loss (mainly gastric) exceeded 5 ml/100 g faeces, the rate of positive benzidine and TMB tests, including the Hemo-Fec Test, varied from 87% to 100%. Fecatest detected half of these cases, whereas Hemoccult II and BM-test-Hemafecia were positive in less than one third. By repeated analyses of faecal specimens stored for 3 days, Fecatest showed a substantially increased sensitivity. We assume that benzidine and TMB tests are sensitive enough to detect occult blood loss from all levels of the gastrointestinal tract, but dietary restrictions are essential to reduce the rate of false-positive tests. Guaiac tests, perhaps with the exception of Fecatest, should be reserved for the detection of occult blood loss from the lower gastrointestinal tract.
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