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At least 415 records · Page 23Linked to original sources

PubMed1995

Test of growth hormone secretion in adults: poor reproducibility of the insulin tolerance test.

The insulin tolerance test (ITT) is regarded as the most reliable provocative test in the diagnosis of growth hormone (GH) deficiency in adults. In the present study the test was evaluated by investigating the range of GH responses in normal adult males and females and the intra-individual reproducibility of the test. Sixteen healthy non-obese adults, eight males (median age 31.5 years) and eight females (median age 31.8 years) were tested twice with the ITT, with a minimum of 72 h between each test. The females were tested between day 3 and day 10 of their menstrual cycles. Adequate hypoglycemia was achieved in all cases with a median nadir blood glucose of 1.3 mmol/l (range 0.8-2.0). Growth hormone in serum was measured by immunoradiometric assay and low values were confirmed by a different assay. Median peak GH concentration responses to the ITT were: in males 27.9 micrograms/l, range 5.0-71.1 (test 1) and 30.5 micrograms/l, range 7.9-69.5 (test 2); and in females 9.0 micrograms/l, range 4.1-17.9 (test 1) and 8.4 micrograms/l, range 0.09-42.4 (test 2). The rise in GH concentration during the ITT was higher in males than in females. In the males, all stimulated GH values were > or = 5.0 micrograms/l. In the females, four out of 16 tests gave values below 5.0 micrograms/l and in one test the GH value was around the detection limit of the assays. There was poor reproducibility during repeated testing, with no correlation between the results of the two tests. The results did not correlate to the magnitude of the hypoglycemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2003

The moderator effect of test anxiety in the relationship between test expectancy and the retention of prose.

The effect of test expectancy and test anxiety on the retention of prose is not yet profoundly examined in an ecologically valid learning context. The influence of test expectancy, test anxiety, and differences in intelligence on the retention of prose was addressed in the hypothesis that test anxiety would act as a moderator between test expectancy and memory retention of prose. Also examined was whether this relation would still be valid if differences in general intelligence were controlled. University freshmen (N=292) participated. Analysis indicated that test anxiety acted as a moderator between test expectancy and prose memory performance, even after controlling for differences in general intelligence. The low and high test-anxious group expecting a retention test seemed to profit from positive arousal elicited by the expectedness of a retention test. The high test-anxious group not expecting a retention test performed in a rather detrimental way on a retention test given negative arousal elicited by the unexpectedness of a retention test. Implications for further research are elaborated and discussed.

Adolescent↗

PubMed2006

Stability of IGF-I concentration despite divergent results of repeated GH stimulating tests indicates poor reproducibility of test results.

OBJECTIVE: Growth hormone (GH) secretion is routinely assessed in provocative tests. However, some limitations of these tests have been reported, including a weak correlation between spontaneous GH secretion and GH peak in stimulating tests, poor reproducibility of test results and normalisation of previously decreased GH response to stimulation in the repeated provocative tests. The observed discrepancies between the results of consecutive GH stimulating tests in the same patient may be explained either by real changes in GH secretion or by the poor reproducibility of GH response to stimulation. Normalisation of previously decreased GH secretion should entail the increase of insulin-like growth factor-I (IGF-I) concentration, while stability of IGF-I secretion despite divergent GH response to stimulation in repeated tests might indicate the poor reproducibility of GH stimulating tests. continue with The aim of the study was a comparison of GH peak in repeated stimulating tests and of corresponding, simultaneously measured IGF-I concentration. METHODS: The investigation comprised 84 children with short stature who underwent repeated GH tests and IGF-I evaluation. In 60 patients each of two different tests (with clonidine and with glucagon, in standard doses) was performed twice, together with IGF-I measurement during both evaluations. In 20 patients (remaining in the same pubertal stage during the time period between the procedures in question) at least one test, together with IGF-I measurement, was repeated within one year. RESULTS: The correlation between the results of GH tests, repeated during the two evaluations, was weak (r=0.22, p<0.05 for all patients and r=0.25, p<0.05 for the patients examined 2 times within 1 year), with the high within-subject variability (43.4 % and 59.5 %, respectively). Conversely, the correlation between two values of IGF-I SDS was good both for all patients (r=0.65, p<0.05) and especially for the patients examined twice within 1 year (r=0.96, p<0.05), with low within-subject variability for the latter subgroup of patients (11.2 %). The same GH stimulating tests, performed twice in the same patient, led to different conclusions (either the confirmation of GHD diagnosis or its exclusion) in most of examined patients. Poor reproducibility of GH stimulating tests, rather than the possibility of short-term changes in GH secretion, was confirmed.

Adolescent↗

PubMed2000

Low-dose (1 microgram) adrenocorticotrophin (ACTH) stimulation as a screening test for impaired hypothalamo-pituitary-adrenal axis function: sensitivity, specificity and accuracy in comparison with the high-dose (250 microgram) test.

OBJECTIVE: We have shown previously that in contrast to the standard high-dose 250-microgram ACTH test, a low-dose 1-microgram ACTH stimulation test correctly identified all patients with pituitary disease who had impaired hypothalamo-pituitary-adrenal (HPA) function. In this study we further compared the performances of these two tests as screening procedures for possible HPA impairment. DESIGN: A comparison of the 1-microgram and the 250-microgram ACTH stimulation tests in healthy controls and in patients with pituitary disease whose HPA axis status was characterized formally by a gold standard test. SUBJECTS: A total of 89 subjects were investigated: 27 healthy normal controls, 43 patients with pituitary disease and normal HPA function, and 19 patients with various pituitary diseases and impaired HPA function. MEASURES: All 89 subjects underwent stimulation with 1 microgram ACTH; 80 also underwent the high-dose 250-microgram ACTH test. A receiver operating characteristic analysis (ROC) was performed to compare the tests. RESULTS: Using a stimulated cortisol > 500 nmol/l as the criterion for a normal response, the 1-microgram ACTH stimulation identified 18 of the 19 subjects with impaired HPA function (94.7% sensitivity with a likelihood ratio of 0.0588 for a negative test). In contrast, 15/16 passed the high-dose test (a 6.2% sensitivity with a likelihood ratio of 0.875 for a negative test). All normal controls, and 36/43 patients with preserved HPA function, passed the 1-microgram ACTH test (90% specificity). This degree of accuracy was unrivalled by the high dose test at all the cut-off levels considered. CONCLUSIONS: More sensitive and accurate, the low-dose 1-microgram ACTH test is as simple and safe as the standard 250-microgram test. We suggest it should replace it in screening for adrenal insufficiency.

Adrenal Insufficiency↗

PubMed2005

Evaluation of a new DNA test compared with the lactose hydrogen breath test for the diagnosis of lactase non-persistence.

BACKGROUND AND AIMS: Recent publications have found that the CC genotype of the DNA variant -13910 T/C upstream of the LCT gene is associated with lactase non-persistence. We therefore compared the value of DNA testing for this variant (DNA test) with the lactose hydrogen breath test (H2 test), which is the clinical standard for the diagnosis of lactase non-persistence. PATIENTS AND METHODS: One hundred and twenty-three consecutive patients with suspected lactose malabsorption were tested for the presence of the -13910 T/C variant by polymerase chain reaction-restriction fragment length polymorphism analysis. These patients also underwent the H2 test after ingestion of 50 g lactose. RESULTS: Thirty-seven subjects had a CC genotype of the -13910 T>C polymorphism suggesting lactase non-persistence; 36 (97%) had also a positive H2 test. Eighty-six subjects had either a TC or a TT genotype suggestive of lactase persistence. Seventy-four (86%) of these tested negative on the H2 test, while 12 patients had a positive H2 test. In eight of these 12 patients duodenal biopsies showed no evidence of small bowel disease. One patient carrying a CC genotype had a negative H2 test. In this patient the rise in serum glucose after oral lactose was normal, furthermore H2 non-excretion was also excluded. CONCLUSIONS: An excellent correlation is observed between a CC genotype and a positive H2 test, whereas the correlation between a TC or TT genotype and a negative H2 test result is less strong. Analysis of the -13910 T/C variant can be considered a good test for predicting the presence of lactase non-persistence in a patient population with suspected lactose malabsorption.

Adolescent↗

PubMed1997

Comparison of serum, salivary, and rapid whole blood diagnostic tests for Helicobacter pylori and their validation against endoscopy based tests.

BACKGROUND: A rapid, reliable, and accurate test for the diagnosis of infection with Helicobacter pylori is needed for screening dyspeptic patients before referral for endoscopy. AIM: To compare a new rapid whole blood test (Helisal rapid blood, Cortecs), two serum enzyme linked immunosorbent assays (ELISAs; Helico-G, Shield and Helisal serum, Cortecs), and a salivary assay (Helisal saliva, Cortecs), with slide biopsy urease, 13C-urea breath test, and histology. METHODS: Three hundred and three consecutive dyspeptic patients attending for gastroscopy underwent two antral biopsies for histology, and one for rapid slide biopsy urease test for assessment of H pylori status. Blood and saliva were also collected. One hundred of the patients also underwent a 13C-urea breath test. Gold standard positives were defined as those with at least two positive tests among slide urease, breath test, or histology, and gold standard negatives as those with all these (or two when the breath test was not done) negative. RESULTS: Of 300 patients (median age 63, range 28-89) eligible for analysis, 137 (46%) were gold standard positives, of which Helisal rapid blood identified 116, Helico-G 129, Helisal serum 130, and Helisal saliva 120; 137 (46%) were gold standard negatives of which the number falsely identified as positive was 30 by Helisal rapid blood, 45 by Helico-G, 41 by Helisal serum, and 41 by Helisal saliva. Sensitivities and specificities were: for the whole blood test 85% and 78% respectively; for Helico-G 94% and 67%, for Helisal serum 95% and 70%, and for Helisal saliva 84% and 70%. CONCLUSIONS: If endoscopy had been undertaken only on patients with positive tests two of 16 duodenal ulcers would have been missed if the Helisal rapid blood test was used, and one if any of the ELISA tests were used. None of the blood tests would have missed any of six gastric ulcers, but the salivary test would have missed one.

Adult↗

PubMed1996

Prediction of psychological functioning one year after the predictive test for Huntington's disease and impact of the test result on reproductive decision making.

For people at risk for Huntington's disease, the anxiety and uncertainty about the future may be very burdensome and may be an obstacle to personal decision making about important life issues, for example, procreation. For some at risk persons, this situation is the reason for requesting predictive DNA testing. The aim of this paper is two-fold. First, we want to evaluate whether knowing one's carrier status reduces anxiety and uncertainty and whether it facilitates decision making about procreation. Second, we endeavour to identify pretest predictors of psychological adaptation one year after the predictive test (psychometric evaluation of general anxiety, depression level, and ego strength). The impact of the predictive test result was assessed in 53 subjects tested, using pre- and post-test psychometric measurement and self-report data of follow up interviews. Mean anxiety and depression levels were significantly decreased one year after a good test result; there was no significant change in the case of a bad test result. The mean personality profile, including ego strength, remained unchanged one year after the test. The study further shows that the test result had a definite impact on reproductive decision making. Stepwise multiple regression analyses were used to select the best predictors of the subject's post-test reactions. The results indicate that a careful evaluation of pretest ego strength, depression level, and coping strategies may be helpful in predicting post-test reactions, independently of the carrier status. Test result (carrier/ non-carrier), gender, and age did not significantly contribute to the prediction. About one third of the variance of post-test anxiety and depression level and more than half of the variance of ego strength was explained, implying that other psychological or social aspects should also be taken into account when predicting individual post-test reactions.

Adult↗

PubMed1999

Micro-column affinity test and gel test: comparative study of two techniques for red cell antibody screening.

BACKGROUND AND OBJECTIVES: We describe the results of a comparative evaluation of a gel test (ID Micro Typing) and a micro-column affinity test (MCAT, Cellbind Screen) for red cell antibody screening and identification under routine conditions. MATERIALS AND METHODS: 3,000 serum samples of patients from the Mannheim University Hospital were tested in parallel by means of the gel test and the MCAT, using the low-ionic-strength-saline indirect antiglobulin test and the protein G affinity technique, respectively. Test cells used were the same in all tests. In addition, we performed titration studies with all detected antibodies as well as with 59 frozen sera containing antibodies of known specificity. RESULTS: A total of 154 antibodies (5.1%) were detected, 149 by gel test and 147 by MCAT. The overall sensitivity and specificity of the gel test was 96.8 and 96.5% and of the MCAT 95.5 and 97.2%. No significant differences between the gel test and MCAT were found when the titer scores of all 213 (fresh and frozen) antibodies were used to check the results. The mean scores for the gel test and the MCAT were 26.8 and 28.5, respectively. For anti-Fy(a) and anti-Kell, a significantly higher titration score could be obtained in the MCAT, whereas anti-Lu(a) showed a significantly higher score with the gel test. CONCLUSION: For the screening of unexpected red blood cell antibodies, the MCAT is as sensitive as the gel indirect antiglobulin test. The sensitivity and specificity of the two systems are more or less the same although it seems that IgM antibodies are better detected by the gel test.

Antibodies, Blocking↗

PubMed2000

Clinical correlates and prognostic significance of six-minute walk test in patients with primary pulmonary hypertension. Comparison with cardiopulmonary exercise testing.

The six-minute walk test is a submaximal exercise test that can be performed even by a patient with heart failure not tolerating maximal exercise testing. To elucidate the clinical significance and prognostic value of the six-minute walk test in patients with primary pulmonary hypertension (PPH), we sought (1) to assess the relation between distance walked during the six-minute walk test and exercise capacity determined by maximal cardiopulmonary exercise testing, and (2) to investigate the prognostic value of the six-minute walk test in comparison with other noninvasive parameters. The six-minute walk test was performed in 43 patients with PPH, together with echocardiography, right heart catheterization, and measurement of plasma epinephrine and norepinephrine. Symptom-limited cardiopulmonary exercise testing was performed in a subsample of patients (n = 27). Distance walked in 6 min was significantly shorter in patients with PPH than in age- and sex-matched healthy subjects (297 +/- 188 versus 655 +/- 91 m, p < 0. 001). The distance significantly decreased in proportion to the severity of New York Heart Association functional class. The distance walked correlated modestly with baseline cardiac output (r = 0.48, p < 0.05) and total pulmonary resistance (r = -0.49, p < 0. 05), but not significantly with mean pulmonary arterial pressure. In contrast, the distance walked correlated strongly with peak V O(2) (r = 0.70, p < 0.001), oxygen pulse (r = 0.57, p < 0.01), and V E-VCO(2) slope (r = -0.66, p < 0.001) determined by cardiopulmonary exercise testing. During a mean follow-up period of 21 +/- 16 mo, 12 patients died of cardiopulmonary causes. Among noninvasive parameters including clinical, echocardiographic, and neurohumoral parameters, only the distance walked in 6 min was independently related to mortality in PPH by multivariate analysis. Patients walking < 332 m had a significantly lower survival rate than those walking farther, assessed by Kaplan-Meier survival curves (log-rank test, p < 0.01). These results suggest that the six-minute walk test, a submaximal exercise test, reflects exercise capacity determined by maximal cardiopulmonary exercise testing in patients with PPH, and it is the distance walked in 6 min that has a strong, independent association with mortality.

Adolescent↗

PubMed1980

Enhanced delayed hypersensitivity skin test reactivity with serial testing in healthy volunteers.

Delayed hypersensitivity skin testing with multiple antigens is frequently used to evaluate immunopotentiation therapy in man. Since serial skin testing with a single antigen has been shown to augment the skin test response, the present study was undertaken to assess the effect of serial delayed hypersensitivity skin testing on skin test reactivity with multiple antigens. Each of twelve healthy volunteers received 0.1 ml of five antigens on two occassion, 6 weeks apart. The antigens used were streptokinase-streptodornase, Candida, Trichophyton, mumps and Mycobacterium tuberculosis (PPD). The results demonstrated enhancement of skin test reactivity in the majority of tests. Indeed, 38.9% of the tests which were negative with the first skin test ( less than 10 mm induration) converted to positive. Enhancement in reactivity was observed in the majority of test subjects with all antigens except PPD. Similar enhanced skin test reactivity was observed in fifteen additional subjects tested serially with Candida only. The observations in this study suggest that uncontrolled studies of immunopotentiation must be interpreted with caution since serial delayed hypersensitivity skin testing with single or multiple antigens results in enhanced skin test reactivity.

Adult↗

PubMed1981

Comparative sensitivity of eight- and 24-hour bile acid breath tests and Schilling test in ileopathies.

The conventional eight-hour bile acid breath test ("acute measurements"), was compared with a modified, extended, 24-hour breath test ("ratio measurements") and the Schilling test to assess relative sensitivity in detecting ileal dysfunction. Sixty-four patients with ileopathies were studied. The presence or absence of bile acid malabsorption was documented by fecal excretion studies of bile acid labels. The sensitivity of the "acute measurements" in the breath test was not significantly different from that of the "ratio measurements" in the ileopathies, regardless of whether or not bile acid malabsorption was present. The "acute measurements" were positive in 49 (77%), the "ratio measurements" in 54 (84%) and the Schilling test in 49 (77%) of the patients. In about 30%, bile acid breath test and Schilling test were not positive in the same patient. A combination of "acute measurements" (breath test) and Schilling test increased the percentage of cases with at least one positive test to 91%. The results of the study show: 1. The sensitivity of the bile acid breath test does not increase if 14CO2 measurements are carried out beyond eight hours. 2. Although the breath test and Schilling test are of similar sensitivity in ileopathies, they are frequently not positive in the same patient. Therefore, it would be clinically useful to combine both tests in order to increase the likelihood of diagnosing ileal dysfunction.

Bile Acids and Salts↗

PubMed1991

Acid perfusion test and 24-hour esophageal pH monitoring with symptom index. Comparison of tests for esophageal acid sensitivity.

The acid perfusion (Bernstein) test and esophageal pH monitoring are the two most popular tests for identifying esophageal acid sensitivity in difficult cases of reflux disease. Therefore, we prospectively compared these test results in 75 consecutive noncardiac chest pain patients who had both an acid perfusion test and chest pain during 24-hr pH testing. A positive acid perfusion test was defined by the replication of the patient's typical chest pain twice by the acid infusion. Esophageal pH testing identified abnormal amounts of acid reflux and correlated symptoms with acid reflux--the "symptom index." Fifteen patients (20%) had a positive acid perfusion test while 45 patients (59%) had a positive symptom index (range 6-100%). Only 9/34 (26%) patients with abnormal reflux had a positive acid perfusion test. Although it had excellent specificity (83-94%), the acid perfusion test had poor sensitivity (32-46%) when compared to the symptom index regardless of the percent positive cutoff level. The best positive predictive value for the acid perfusion test was 87%, but this occurred when the test sensitivity was 32%. Modifying the end point of a positive acid perfusion test to include heartburn improves the sensitivity (52-67%) while markedly compromising specificity and positive predictive value. Thus, esophageal pH monitoring correlating symptoms with acid reflux is superior to the acid perfusion test for identifying an acid sensitive esophagus in patients with noncardiac chest pain.

Chest Pain↗

PubMed1994

[Value of the patient's own test substances in epicutaneous testing].

Patch testing with commercially available test kits of known allergens often leads to detection of the responsible allergen. In many cases, however, the responsible allergen cannot be found unless the patient's "own" products or chemicals are tested. An analysis of 2460 patch tests with patch test kits proposed by the DKG (German Contact Allergy Group) and a positive history of a patient's own substance showed positive results in 208 patients with 289 products. In 44% (129 out of 289) the responsible allergen could only be found by testing the patient's own substances, in 56% (160 out of 289) the same allergen as was responsible for the positive result with patients' endogenous substances was positive in one of the commercially available test kits. The substances that tested positive were medical products/adhesives (45%), cosmetics (39.4%), rubber materials (4.1%), leather materials (0.7%) and others (10%). Subsequent testing of the different components of the patients' own substances that tested positive was carried out in 45 cases and resulted in the detection of new allergens, such as tris-(2-hydroxyethyl)isocyanurate triacrylate. In 27 patients the endogenous substances had tested positive in the course of testing for occupational dermatitis, and in 10 of these positive testing of a patient's own product resulted in notification of an occupational dermatitis. These results show, that patch testing with the patients own products if very important for the finding of the responsible or even new allergens.

Adult↗

PubMed1984

Genotoxic activity and potency of 135 compounds in the Ames reversion test and in a bacterial DNA-repair test.

Compounds of various chemical classes were comparatively assayed in the Ames reversion test with his- S. typhimurium strains TA1535, TA157 , TA1538, TA98, TA100, and, in part, TA97 , and in a DNA-repair test with trp- E. coli strains WP2 (repair-proficient), WP67 (uvrA- polA-) and CM871 (uvrA- recA- lexA-). A liquid micromethod procedure for the assessment of the minimal inhibitory concentration (MIC) of test compounds, using the same reagents as the Ames test, was set up and calibrated in its technical details. Other techniques (spot test and treat-and-plate method) were applied to a number of compounds in order to obtain more complete information on their DNA-damaging activity in E. coli. From a qualitative standpoint, the results obtained in the reversion test and in the DNA-repair test (liquid micromethod) were overlapping for 96 (59 positive and 37 negative) out of 135 compounds (71.1%). There was disagreement for 39 compounds (28.9%), 9 of which were positive only in the reversion test (8 requiring metabolic activation and 5 genotoxic in the treat-and-plate method). 30 compounds were positive only in the lethality test, showing a direct DNA-damaging activity, which in half of the cases was completely eliminated by S9 mix. Although the experimental protocol intentionally included several compounds already reported as nonmutagenic carcinogens or as noncarcinogenic mutagens, the overall accuracy was 64.5% for the reversion test and 72.4% for the DNA-repair test, as evaluated for 75 compounds classified according to their carcinogenic activity. Quantitation of results was obtained in the Ames test by relating the net number of revertants to nmoles of compound and in the DNA-repair test by means of a formula relating the difference and ratio of MICs in repair-proficient and -deficient bacteria to nmoles of compound. Following these criteria, the genotoxic potency varied over a 4.5 X 10(7)-fold range among compounds positive in the reversion test and over a 6 X 10(9)-fold range among compounds damaging E. coli DNA. The genotoxic potencies in the two bacterial systems were correlated within the majority of the chemical classes under scrutiny.

Biotransformation↗

PubMed1991

The genotoxicities of N-nitrosamines in Drosophila melanogaster in vivo: the correlation of mutagenicity in the wing spot test with the DNA damages detected by the DNA-repair test.

The genotoxicities of a series of N-nitrosamines were assayed in the wing spot test and a new short-term test of Drosophila melanogaster. In the spot test, larval flies trans-heterozygous for the somatic cell markers mwh and flr3 were fed the test reagents and the wing hairs in adults were inspected for clones expressing the phenotypes of the markers. In the other test, larval stock consisting of meiotic recombination-deficient (Rec-) double mutant mei-9a and mei-41D5 males and repair-proficient Rec+ females were grown on feed containing the reagents and the DNA damages were detected with the preferential killing of the Rec- larvae as an endpoint. The carcinogenic nitrosamines tested, N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-butylamine (NDBA), N-nitrosomorpholine (NMOR), N-nitro-sopiperidine (NPIP) and N-nitrosopyrrolidine (NPYR), all showed clearly positive activities in both tests. The activities in the wing spot test were ranked in a sequence of NDMA much greater than NMOR greater than NPIP greater than NDEA greater than NPYR greater than NDBA. A similar ranking was obtained in the repair assay. The genotoxicity of N-nitrosodiphenylamine (NDPhA), carcinogenicity studies of which are inconclusive, was marginal in the spot test. The non-carcinogenic N-nitrosoproline (NPRO) and the non-mutagenic N-nitrosothioproline (NTPRO) were negative in the spot test. NDPhA and NPRO were negative in the repair test as well. The DNA-repair test is thus a convenient technique for estimating the mutagenicity of compounds because of its simplicity compared with the wing spot test. These Drosophila tests may be useful in predicting carcinogenic potentials of compounds.

Animals↗

PubMed1994

Modified suspension Ames test for testing proteinaceous substances: an initial step.

The basic Salmonella/microsome assay (Ames test) is a valuable primary tool by which to discriminate mutagens from non-mutagens. For a variety of chemical test substances this test is easily conducted according to international guidelines for genotoxicity testing. However, the testing of proteinaceous substances in the basic Ames test may generate false positives owing to the presence of growth-promoting constituents in the test sample, such as histidine or its precursors. It was hypothesized that the growth-promoting capacities of biological test samples might be overcome by testing according to the 'suspension variant' of the Ames test, which uses very rich growth conditions thereby overwhelming any growth-enhancing constituents present in a biological test sample. This hypothesis appeared to be correct, although several important modifications had to be made to the suspension assay. The most important aspect of this 'new suspension Ames test' appeared to be the plating of overnight regrown bacteria in the poorest way possible (by omitting histidine and nutrient broth from the overlay agar). This study may comprise an initial step in the development of a modified suspension Ames test for testing proteinaceous substances.

False Positive Reactions↗

PubMed2004

Influence of test temperature and test speed on the mechanical strength of absorbable suture anchors.

PURPOSE: Absorbable implant materials offer various advantages but are mechanically far weaker than metals. Despite known temperature dependence of the biomechanical properties of these materials, mechanical testing has almost exclusively been performed at room temperature in the literature. In this study, the difference in mechanical performance at room and body temperature was assessed in vitro at different test speeds. TYPE OF STUDY: Biomechanical bench study. METHODS: Five absorbable suture anchor models were held in a metallic holder and loaded under tension using 0.5-mm steel wires until failure. Testing temperature was 20 degrees C +/- 1 degrees C or 37 degrees C +/- 1 degrees C, test speed was 50 mm/min or 5 mm/min. Tensile load at failure and failure mode were recorded. To test creep behavior, a constant load of 100 N was applied, and time to failure was recorded at both temperatures. RESULTS: Both raising the temperature and decreasing test speed significantly (P <.0001) impaired the mechanical performance of the tested implants. Increase of temperature (20 degrees C to 37 degrees C) resulted in a decrease of the maximal failure strength by up to 40% and decreased time to failure by up to 98% under static load. At 37 degrees, decreasing the test speed from 50 to 5 mm/min lowered the load to failure by up to 18%. Failure of the anchors always occurred by eyelet cutout of the wire. CONCLUSIONS: The lower the test speed, the higher is the influence of the testing temperature. Testing of implants at room temperature instead of body temperature may falsely improve test results by a factor of up to 50 under static load. Therefore, testing absorbable implants at body temperature seems mandatory, preferably at slow test speeds.

Absorbable Implants↗

PubMed2005

The use of behavioral test batteries, II: effect of test interval.

Test batteries are commonly used to assess the behavioral phenotype of genetically modified and inbred strains of mice. However, few systematic studies have been employed to address several key issues concerning the use of a test battery. The current study was designed to address whether inter-test interval affects behavioral performance. Male mice of 3 different inbred strains and one F1 hybrid strain were randomly assigned to either a test battery with 1 week inter-test intervals, or a rapid test battery with 1-2 day inter-test intervals. The test battery included a neurological exam, open-field activity, light-dark exploration, rotarod test, prepulse inhibition, and startle habituation. The experiment was repeated with female animals of 2 different strains. As expected, there were strain differences on each of the behavioral assays; however, there was no major difference in performance between mice of the standard test battery and the rapid test battery. Similar results were found with females. These results indicate that the interval between most tests could be as little as 1-2 days, with little significant effect on overall performance. Thus, it is possible with the current test battery to reduce the inter-test interval to facilitate the rate of studying and identifying behavioral phenotypes in mice.

Analysis of Variance↗