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PubMed1977

Experimental investigations in guinea pigs on the recognition of the allergic eczematous reaction: A comparison of the macrophage migration inhibition test with the patch test.

1. The patch test as an in vivo test has disadvantages. It is our impression that biologically false reactions occur in approximately 5%. 2. The MIT as an in vitro test is very time consuming, but safe for the patient. It is supposed to give up to 20% false reactions. 3. In 76 and 72% of 156 guinea pigs sensitized with potassium bichromate and sulfasol respectively, both the test methods gave results in agreement. 4. Sensitization by potassium bichromate estimated by patch test only was 30%, and by MIT only also 30%, but the two test methods disagreed in 24%. 5. Sensitization by sulfasol evaluated in the patch test only was 36%, and in the MIT only 48% but the two test methods disagreed in 28%. 6. The differences between the results of the two test methods are not satistically significant and their failure rate does not provide absolutely sure results, but we believe that the patch test is preferrable in recognition of contact allergy because it is in vivo and probably has a lower failure rate in comparison with the MIT in the human.

Animals↗
PubMed2005

[The external quality assessment for Mycobacterium tuberculosis drug susceptibility testing by proficiency testing panel to the commercial laboratories].

OBJECTIVE: The Committee for Mycobacterial Examinations has programmed and implemented the external quality assessment for Mycobacterium tuberculosis drug susceptibility testing by proficiency testing panel to the commercial laboratories that perform drug susceptibility testing more than 20 cases monthly. METHOD: It utilized 20 strains, exactly pairs of 10 strains, of Mycobacterium tuberculosis that were evaluated for the resistance pattern in the WHO/IUATLD supra-national laboratory network (SRLN), and the concordant results within SRLN were employed as the gold standard of the test. Each laboratory performed the drug susceptibility testing with routine method including the preparation of bacterial suspension. RESULTS: As a result, the sensitivity for isoniazid (INH) was 95% on an average, ranging from 29% to 100%. The specificity and efficiency for INH were 100% and 97% (50-100), respectively. Additionally, the reproducibility for INH was 99% (90-100). Similarly, the sensitivity, specificity, efficiency and reproducibility for rifampicin (RFP) were 95% (63-100), 99% (67-100), 97% (70-100) and 98% (90-100), respectively. The sensitivity, specificity, efficiency and reproducibility for streptomycin (SM) were 66% (33-100), 94% (64-100), 86% (65-100) and 96% (80-100), respectively. For EB, the sensitivity, specificity, efficiency and reproducibility were 96% (33-100), 74% (57-86), 81% (60-90) and 96% (80-100), respectively. DISCUSSION: The required standard for satisfactory results of sensitivity, specificity and reproducibility is 95%, and the results for INH and RFP were excellent on an average. However, several laboratories showed unsatisfactory results, especially in sensitivity. Almost all the discordant results for INH and RFP were false-susceptible comparing to the gold standard. For INH, one pair of tested strain showed discordant results in many evaluated laboratories and seemed to reflect the relatively low concordance even in SRLN. On the other hand, the reason for false-susceptible results for RFP was unclear. Several laboratories showed discordant results in one strain pair so that it might be a technical mistake. The sensitivity of SM was remarkably low and it was due to many false-susceptible results, which was twice the number of false-resistance. It was due to the character of tested strain partially considering relatively low concordance in SRLN. However, there was no persuasive explanation for the inconsistency in other strains that showed highly concordant results in SRLN. The difference of critical drug concentration in Lowenstein-Jensen and 1% Ogawa medium might contribute to the discrepancies. The specificity of EB was low and it was due to many false-resistant results. About a specific pair of tested strain, almost 100% of laboratories showed concordant false-resistant results whereas SRLN showed perfectly concordant susceptible result. If this strain was considered as resistant and another strain that showed less than 70% concordance in the tested laboratories was excluded, the sensitivity, specificity and efficiency would improve to 96%, 97% and 97%, respectively. The proficiency testing is a part of external quality assessment system and requires following corrective actions. A permanent quality improvement and maintenance will be expected through the spiral circulation of quality assurance activities.

Antitubercular Agents↗
PubMed1978

A comparison between the macrophage migration inhibition test (MMI) and the leucocyte adherence inhibition test (LAI) in patients with melanoma and carcinoma of the colon.

Patients with progressing tumours have circulating leucocytes which are sensitised to tumour specific antigens and their serum contains blocking factors. Patients who have tumours which have been successfully destroyed do not have circulating blocking factors although their lymphocytes continue to remain sensitised to the tumour antigens. Two tests, known to detect cellular sensitisation and serum blocking activity, the leucocyte adherence inhibition test (LAI) and the macrophage migration inhibition test (MMI) have been compared in a small group of patients with malignant melanoma and carcinoma of the colon. There was agreement between the results of both tests in over three-quarters of the tests performed and in those which failed to agree neither test was favoured in relation to the known tumour state of the patient. Thirty-two tests were performed in 22 patients, there was one false positive with MMI testing, seven false negative results for the LAI test and six for the MMI test.

Animals↗
PubMed1983

Early submaximal exercise stress test after myocardial infarction. Comparison with a late test and prognostic value.

An early exercise stress test was carried out in 116 patients 8 to 14 days after a myocardial infarction. This test is in good agreement with the late maximal stress test performed 8 weeks after the infarction, both tests being positive together in 86.4% and negative in 84.6% of the cases. Residual coronary insufficiency is present in 41.4% of the patients during the early test, 47.9% after inferior and 30.2% after anterior infarction. With beta blocking therapy, 28.2% of the patients had a positive test, and 48% without this treatment. The sensitivity of the early test is good after inferior infarction but poor after anterior infarction or during beta blocking therapy. A multivessel disease is disclosed by coronary angiography in 78.5% of the patients with a positive early stress test and in 53.3% in cases with a negative test. In the patients with a positive test, mortality at one year is higher (8.7% versus 2.9%). A coronary angiography should be performed relatively precociously in this group of patients.

Adrenergic beta-Antagonists↗
PubMed1980

[Comparison of the Limulus test with the pyrogen test in rabbits].

The Limulus test was compared with the official pyrogen test in rabbits for detecting pyrogens in medical devices for single use. 46 samples were examined. Two of them were positive in the rabbit test and also in the Limulus test; 5 samples were only positive in the Limulus test. This is in agreement with published papers. Against endotoxins of gram-negative bacteria the Limulus test is more sensitive than the common test in rabbits, but not sensitive for other pyrogens. Therefore, the Limulus test cannot replace the official rabbit test in the quality control of medical devices. We recommend the Limulus test as a quick, simple and highly sensitive screening method for gram-negative bacterial endotoxins, the most common pyrogen contaminants in drugs.

Animals↗
PubMed1978

The thymol turbidity test and determination of serum cholesterol : two tests to abandon in the routine evaluation of liver function.

The thymol turbidity test (Macglan's test) and the determination of serum cholesterol are still performed routinely as liver function tests in many laboratories. In this report, we have employed quantitative methods in order to evaluate the real usefulness of these two parameters. In a first step, the value of the thymol test and of cholesterol determination for the discrimination of the 13 most frequent hepato-biliary diseases was studied by analysis of variance, and compared to that of the following tests : serum bilirubin, serum glutamic pyruvic transaminase, serum alkaline phosphatase serum protein electrophoresis and prothrombin time. It was found that of all these parameters, the thymol test and cholesterol measurement had the lowest discriminatory powers. In a second step, the consequences of the suppression of the two tests were examined by linear discrimination analysis, which was done for all the possible pairs of diseases. It appeared that in each case, the loss of information due to the elimination of the thymol test or of cholesterol determination was nil or negligible. We conclude therefore that the thymol turbidity test and determination of serum cholesterol should be abandoned as routine tests of liver function.

Cholesterol↗
PubMed1995

[Model calculations for HIV screening of blood and plasma donors with a combination of 2 screening tests: test strategies, validity, costs and effectiveness].

OBJECTIVE: The strategies for combining two screening tests for HIV infections in blood or plasma donors are formulated in biometric terms and analyzed with respect to their value, i.e. their validity, cost and effectiveness. DESIGN: Biometrical modeling using assumptions on the validity of the single tests, the conditional correlations between them, as well as on the cost of testing and the consequences of false-negative or false-positive test results. RESULTS: If the test combination is defined as positive whenever at least one of the single tests is positive, then this rule (the 'believe the positive' rule, BTP), due to its lower specificity, has extremely low positive predictive values. In case of high prevalence rates of the infection (e.g. 1:1,000), the BTP rule leads to lower total cost than single testing, unless the latter has very high sensitivity (e.g. 99%). For smaller prevalence rates (< 1:50,000), which are more typical of the selected group of blood or plasma donors, combination testing is of little value because the extra cost of detecting one additional infection (compared with single testing) may reach several 100 million DM. CONCLUSION: The cost for detecting additional cases of HIV infection by using combination instead of single testing in HIV screening is so high that this decision requires a public consensus.

AIDS Serodiagnosis↗
PubMed1993

Drug-testing methods and clinical interpretations of test results.

In the present paper, major issues related to drug testing are discussed. For example, drug-testing techniques measure the presence of a drug or drugs but are not sophisticated enough to measure impairment from drug use. Moreover, it is difficult to determine the route of drug administration, quantity or frequency, as well as when the drug was taken, on the basis of the laboratory results. Selection of the drug to be tested should depend on the local availability of the drug, its abuse potential and clinical effects, as well as on the availability of analytical technology and expertise in testing and in interpreting laboratory results. The most sophisticated drug-testing approach is gas chromatography coupled with mass spectrometry (GC/MS), which is regarded as a "gold standard"; it is used in confirmatory testing. Typically, GC/MS is preceded by a rapid immunoassay method to eliminate the majority of the "negative" samples. Despite the existence of sophisticated drug-testing methods, it is still possible to obtain incorrect test results. Such results may be caused by the presence of interfering substances or adulteration of the urine sample. A number of techniques can be employed to reduce the likelihood of obtaining erroneous results and to detect adulterated urine samples. A "positive" drug finding can have a serious impact on the livelihood of an individual, therefore, persons conducting such tests should adhere to the strictest standards of laboratory performance. Only qualified and experienced individuals with proper laboratory equipment should perform these analyses. The standards of laboratory performance must meet local legal and forensic requirements. Access to patient samples and laboratory records must be restricted in order to prevent the tampering of samples and results. In order to maintain confidentiality, the results must be communicated only to the medical review officer. Chain-of-custody documents and all file so that they can be examined in case of a legal challenge. The laboratory must have a complete record on quality control. Finally, specific initial and confirmatory testing requirements should be met.

Bias↗
PubMed1996

Assessment of the influence of hydrogen nonexcretion on the usefulness of the hydrogen breath test and lactose tolerance test.

The recognition of hydrogen nonexcretion in up to 20% of tested subjects and the large ethnic differences in the prevalence of lactose malabsorption make it necessary to reassess the diagnostic usefulness of the lactose tolerance test and the hydrogen breath test. Both tests were performed in 83 consecutive patients with suspected lactose malabsorption who ingested 50 g lactose. On a separate day a hydrogen breath test was performed after 25 g lactulose. The prevalence of hydrogen nonexcretion was 18%. The diagnostic usefulness of hydrogen breath test was influenced both by the individual threshold for hydrogen excretion and the amount of malabsorbed lactose. In addition to baseline values, breath samples for hydrogen measurements have to be taken at 30, 60, 90, 180, and 240 minutes after ingestion of lactose. For the lactose tolerance test only one measurement of serum glucose at 30 minutes is needed in addition to the baseline measurement. The combination of both tests excludes the influence of hydrogen nonexcretion, but even if a combined diagnostic approach utilizing the lactose hydrogen breath test and lactose tolerance test is used, 6% of patients presenting with symptoms suggestive of lactose intolerance cannot be classified.

Adolescent↗
PubMed1977

Completion of hemagglutination inhibition test by solid-phase radioimmunoassay test in routine diagnostic rubella serology.

A solid-phase radioimmunoassay (RIA) test for rubella virus IgG and IgM class antibodies was used for completing the hemagglutination inhibition (HI) test in routine diagnostic serology. During a six-month period 80 serum specimens from 47 patients were tested by RIA because the HI test result was either unreliable or gave insufficient information. This was approximately 5% of the total number of serum specimens tested for rubella antibodies in our laboratory during the study period. The main indications for using the RIA test were improper timing in the taking of serum specimens, which accounted for IgM determination, and nonspecific agglutinins or nonspecific serum hemaglutination inhibitors, which disturbed the HI test. In all cases an unambiguous result was obtained by the RIA test, and five recent rubella infections, not diagnosably by the HI test, were detected. Based on these findings we consider the RIA test to be a good alternative among the methods proposed for diagnostic rubella serology.

Hemagglutination Inhibition Tests↗
PubMed1997

Comparison of dobutamine electrocardiographic stress test and exercise test in two different groups of patients with unstable angina.

Exercise testing is a well known means of evaluating patients with unstable angina, but in recent years, alternative methods have been proposed. We prospectively compared standard exercise testing with dobutamine electrocardiographic stress testing for patients who were admitted with a diagnosis of unstable angina. A total of 43 patients were studied, divided into two different groups, according to the presence (group A n = 26) or absence (group B n = 17) of a previous history of coronary artery disease and/or electrocardiographic changes compatible with ischemia on admission. Dobutamine electrocardiographic stress testing was performed in a standard manner at 3 +/- 1 days after admission in group A and at 16 +/- 8 hours after admission in group B. Exercise testing was performed, on average 5 +/- 1 days following the event in group A and 2 days after admission in group B. Agreement between both tests was observed in 39 (91%) cases, Kappa value: 0.81. The dobutamine test predicted the result of the exercise test with a sensitivity of 79% (95% CI 54-90), and a specificity of 100% (95% CI 86-100), with a positive predictive value of 100% and a negative predictive value of 86%. It can be concluded that dobutamine electrocardiographic stress testing is an objective and reliable procedure that accurately predicts the results of standard exercise testing in patients with a diagnosis of unstable angina. If this result were confirmed with a greater number of patients, it would be a good option for definitive diagnosis and risk stratification, in addition to being inexpensive and easy to perform. It can also be particularly useful for patients who cannot perform exercise.

Adult↗
PubMed1998

E-test for susceptibility testing of Mycobacterium tuberculosis.

SETTING: Initial isolates should be tested for drug susceptibility to confirm the anticipated effectiveness of chemotherapy. OBJECTIVE: To evaluate E-test strips for susceptibility testing of Mycobacterium tuberculosis. DESIGN: A proportion method using Lowenstein-Jensen medium and the Bactec radiometric system were compared with the E-test (isoniazid [INH], rifampicin [RMP], ethambutol [EMB] and streptomycin [SM]). RESULTS: For 73 of the 81 M. tuberculosis isolates (90.1%) the proportion and E-test methods yielded concordant susceptibility results against all four antimicrobial agents tested. Of these 73 strains, 69 were fully susceptible; the four isolates showing resistance to antimicrobial drugs by both methods were also resistant when tested by Bactec 460TB. While the proportion method indicated susceptibility for the eight remaining strains, E-test results showed mono EMB resistance in five strains, INH resistance for two isolates (including one isolate resistant to EMB plus INH), and for one strain E-test yielded resistance to EMB and SM. Using Bactec as the reference method, the E-test resulted in false resistance in eight strains and no false susceptibility. CONCLUSION: Due to a substantial rate of false resistance, this method cannot be recommended at present for practical use in clinical laboratories.

False Negative Reactions↗
PubMed1998

Patch testing reactions to a standard series in 608 patients tested from 1990 to 1997 at Massachusetts General Hospital.

BACKGROUND: Patch testing is a useful diagnostic tool when allergic contact dermatitis is suspected clinically. OBJECTIVE: This study describes the results of patch testing performed from January 1, 1990 to June 1, 1997 at the Massachusetts General Hospital Contact Dermatitis Clinic. The findings are compared with those previously reported by the North American Contact Dermatitis Group (NACDG). METHODS: Data were collected from chart review and analyzed. Patients included in the study underwent patch testing to the full European standard series of allergens. A standardized patch testing technique was used, and readings were performed by a single observer. RESULTS: A total of 608 patients were patch tested to a screening tray of 24 allergens; 69.9% were women. At least one positive patch test reaction was observed in 60.0% of patients. The most common sensitizers were nickel sulfate, fragrance mix, potassium dichromate, cobalt chloride, balsam of Peru, quaternium-15, and neomycin sulfate. The sensitization rate to potassium dichromate (9.4%) was higher than has been reported by the NACDG. A statistically significant difference in the sensitization rate in men and women was observed for nickel, quinoline mix, epoxy resin, and formaldehyde. The prevalence of positive patch test reactions was not found to be influenced by testing during the summer months. CONCLUSIONS: In the authors' opinion, the prevalence of contact sensitization is generally comparable with the findings of the NACDG, with the exception of reactions to potassium dichromate. This difference in results probably reflects, in part, differences in methodology. The test concentration of potassium dichromate was 0.5%, commonly used in Europe, instead of the 0.25% concentration used by the NACDG. Further investigation is necessary to determine the optimal testing concentration of potassium dichromate.

Adolescent↗
PubMed1998

Prognostic patch testing: the other kind of patch test.

Prognostic patch testing differs from diagnostic patch testing. Clinicians routinely perform diagnostic patch testing, but prognotic patch testing is the province of corporate research and development departments and, in the United States, contract laboratories. The three types of prognostic patch testing are described and referenced in the scientific and medical literature. A comparison among the three types of prognostic patch testing and diagnostic patch testing is provided. In addition, the variables in both prognostic and diagnostic patch testing are listed, as well as the types of ingredients and products routinely tested in prognostic patch testing.

Consumer Product Safety↗
PubMed2004

Diagnostic test accuracy and prevalence inferences based on joint and sequential testing with finite population sampling.

The two-test two-population model, originally formulated by Hui and Walter, for estimation of test accuracy and prevalence estimation assumes conditionally independent tests, constant accuracy across populations and binomial sampling. The binomial assumption is incorrect if all individuals in a population e.g. child-care centre, village in Africa, or a cattle herd are sampled or if the sample size is large relative to population size. In this paper, we develop statistical methods for evaluating diagnostic test accuracy and prevalence estimation based on finite sample data in the absence of a gold standard. Moreover, two tests are often applied simultaneously for the purpose of obtaining a 'joint' testing strategy that has either higher overall sensitivity or specificity than either of the two tests considered singly. Sequential versions of such strategies are often applied in order to reduce the cost of testing. We thus discuss joint (simultaneous and sequential) testing strategies and inference for them. Using the developed methods, we analyse two real and one simulated data sets, and we compare 'hypergeometric' and 'binomial-based' inferences. Our findings indicate that the posterior standard deviations for prevalence (but not sensitivity and specificity) based on finite population sampling tend to be smaller than their counterparts for infinite population sampling. Finally, we make recommendations about how small the sample size should be relative to the population size to warrant use of the binomial model for prevalence estimation.

Agglutination Tests↗
PubMed1976

The Kveim test: analysis of results of tests using colindale (K 12) materials.

Results of an analysis are presented of the salient clinical, pathological, and Kveim-test data of importance in the diagnostic assessment of 839 patients in whom a Kveim test was made as part of their routine clinical investigation. From these analyses the following significant observations can be made: 1) The age distribution and negative tuberculin results in patients with sarcoidosis were in keeping with the diagnosis of sarcoidosis, whereas for those in whom a diagnosis other than sarcoidosis was made, they were not. 2) The findings of 64% positive tuberculin results in cases of confirmed sarcoidosis of less than 2 yr known duration and only 39% in those of greater than 2 yr duration are closely similar to those found in international Kveim-test studies reported by Siltzbach in 1966 and Hurley and Bartholomeusz in 1971. 3) The use of the material was helpful in confirming a diagnosis of sarcoidosis in patients with extrathoracic lesions, for positive results were obtained in 33% of those with uveitis 40% of those with erythema nodosum only (findings which are in keeping with those of other studies in the United Kingdom, and 60% among 27 patients presenting with lesions in various sites, including 2 with cranial nerve lesions and one with cardiac arrhythmia. 4) We found only 2 positive reactions (less than 1%) among 221 patients in whom a diagnosis other than sarcoidosis was reached. Clearly these findings show that the Kveim test material. Lots 19 and 22, of spleen K 12 exhibited not only a high degree of reactivity and selectivity for sarcoidosis, but also that they were of considerable practical value as an aid to diagnosis. The finding of only 2(0.9%) positive Kveim tests among 221 patients with diseases other than sarcoidosis is of special interest. Of the different diseases that were ultimately diagnosed only 6 patients tested had lymphoma, only 11 had either pulmonary or lymphatic tuberculosis, and only one had Crohn's disease. Although these numbers are small, it is relevant to compare the Kveim-test data of Lots 19 and 22 of K 12 with those of Lot 5 and of Lot 14 of the same spleen. In validation studies Lot 5 yielded the expected proportion of positive reactions at different stages of sarcoidosis and a negligible proportion of positive reactions with active or quiescent pulmonary tuberculosis or among healthy subjects. However, in subsequent studies in special groups of patients, those with Crohn's disease, ulcerative colitis, or lymphatic tuberculosis, a proportion of the Kveim tests performed with these lots were positive. Within the context of the present field study, the results of these analyses confirm that the last lots of K 12 material exhibited a high degree of selectivity for sarcoidosis and that they emphasize again the practical value of the Kveim tests with suspensions that have undergone careful validation.

Adolescent↗
PubMed1984

Quantitation of enterovirus 70 antibody by microneutralization test and comparison with standard neutralization, hemagglutination inhibition, and complement fixation tests with different virus strains.

We describe here a microneutralization procedure for conveniently testing large numbers of specimens for antibodies to enterovirus 70. The test utilized human rhabdomyosarcoma cells and was read by staining with crystal violet after 4 days of incubation. The test compares well with other serological assays, being more sensitive than the standard tube neutralization test and the complement fixation test, but less sensitive than the hemagglutination inhibition test. However, the hemagglutination inhibition test required concentrated, partially purified virus as antigen, as did the complement fixation test, and was difficult to read, so that its greater sensitivity may not be of practical significance. By all four test procedures, a recent isolate of enterovirus 70 was a more sensitive antigen than the prototype strain, as shown by greater geometric mean titers in sera of patients from various epidemics.

Antibodies, Viral↗
PubMed1999

Uptake of genetic testing and pre-test levels of mental distress in Norwegian families with known BRCA1 mutations.

232 family members from 27 Norwegian families with BRCA1 mutations were offered genetic testing. 180/232 (78%) chose to be tested, 14/232 (6%) have not yet decided and 38/232 (16%) declined. All 232 persons were invited to fill in the following questionnaires when offered testing: Impact of Event Scale (IES), Hospital Anxiety and Depression Scale (HADS), General Health Questionnaire (GHQ-28) and Beck Hopelessness Scale (BHS). 207/232 (89%) responded to the questionnaires. Of those declining to be tested 23/38 (61%) answered the questionnaires compared to 170/180 (94%) of those wanting the test (p < 0.0001). A higher proportion of females with a history of cancer than females without such a history had abnormal scores on the IES-intrusion and GHQ questionnaires (p < 0.001). Healthy females who were deciding on predictive testing had the same or lower prevalence of mental distress compared to the general population, between 4.3% and 18.0% as measured by the different questionnaires. Males did not differ from healthy females on any of the measures. According to their HADS scores, women without a history of cancer deciding on predictive testing for breast-ovarian cancer had lower or equal levels of mental distress compared to the general population. The high uptake of genetic testing combined with the lower than normal prevalence of mental distress indicates that the activity may continue as practised, awaiting longitudinal data concerning the levels of mental distress after genetic testing.

Anxiety↗