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PubMed1987

[The Schilling test in Biermer's disease, problems of false negative reactions. Apropos of a case].

A case of pernicious anemia in a 30 years old men is described. This disease was typical for the hematologic, immunologic and medullary patterns, for his evolution, but the Schilling test, a dual tracer method, did not confirm the diagnosis. The contradictory of this result can be explained wether by the bias of the test itself, or by the intestinal malabsorption due to the vitamin B12 deficiency, or by other factors like bacterial overgrowth state (associated in the pernicious anemia) and a high level of antibodies to intrinsic factor.

Adult↗
PubMed2002

[Systematic reviews in practice. X. Searching, selecting and the methodological assessment of diagnostic evaluation research].

Literature concerning the value of diagnostic tests is poorly indexed in electronic bibliographical databases. An extensive, sensitive and specific search strategy for evaluation of a diagnostic test in Medline is a combination of key words or text words concerning the diagnostic test with: 'sensitivity and specificity' (exploded), 'mass screening' (exploded), 'reference values', 'false positive reactions', 'false negative reactions', 'specificit$.tw', 'screening.tw', 'false positive$.tw', 'false negative$.tw', 'accuracy.tw', 'predictive value$.tw', 'reference value$.tw', 'roc$.tw' or 'likelihood ratio$.tw'. Inclusion and exclusion criteria select publications which meet certain minimum requirements, such as the presence of an accepted reference standard, a clear definition of 'diseased', and the presence of a suitable outcome measure. The methodological assessment list should contain a number of validity criteria as well as a number of criteria by which to measure the extent to which the study results can be generalised. Important assessment criteria that may affect the diagnostic value of the test are: study design, blinding, use of different reference standards, the absence of details about the diagnostic criteria for the diagnostic test and insufficient information about the study population.

Diagnostic Tests, Routine↗
PubMed1983

HLA typing of cultured amniotic fluid cells.

HLA typing was performed on 18 cultures of human amniotic fluid cells using cytotoxicity and absorption technics. Confirmation of antigen assignments was obtained in nine of ten instances, where HLA typing also was performed on cord blood. Three major problems were encountered in performing these studies: (1) complement cytotoxicity, (2) false-positive reactions, and (3) false-negative reactions. False-positive and false-negative reactions occurred more frequently with sera defining HLA-B locus specificities than with sera defining HLA-A locus specificities. Absorption studies were helpful in making antigen assignments when false reactions occurred. Preliminary studies suggest that the frequency of false-positive reactions can be decreased by absorbing HLA typing sera with antigen-negative amniotic fluid cultured cells, buffy coat, or platelets. Accurate antigen assignment is difficult when parental HLA types are unavailable.

Absorption↗
PubMed1978

The diagnostic efficiency of some serological tests for bovine brucellosis.

Results obtained from 1887 sera using three serological tests for bovine brucellosis were compared with a serological classification of sera described as the 'probable infection status'. Sera showing apparent false positive and apparent false negative reactions were identified, and were subjected to supplementary testing as appropriate. The serum agglutination test (SAT) gave 35% apparent false negative reactions and 5% apparent false positives. The complement fixation test (CFT) gave 12% apparent false negative reactions using warm fixation (CFTW) and at least 5% using cold fixation (CFTC). The routine diagnostic system used in Victoria, in which the CFTW is supplemented by the CFTC and the SAT, gave 9% apparent false negative reactions and 2% apparent false positive reactions. The radioimmunoassay gave 1% or 6% apparent false negative reactions, depending on the minimum diagnostic value used. Atypical reactions in the CFT sometimes caused difficulties in diagnosis.

Agglutination Tests↗
PubMed1976

Predictive value of cross-matching for transfusion of platelet concentrates to alloimmunized recipients.

Compatibility tests in which donor platelets were tested with recipient sera were performed retroactively after 64 transfusions of platelets from 59 unrelated donors to 10 alloimmunized patients. Techniques used were serotonin release, aggregometry, platelet factor 3 release, and lymphocytotoxicity, each of which has been advocated as a means of testing donor-recipient platelet compatibility. Although "false positive" reactions were few (positive crossmatch but satisfactory transfusion response), "false negative" reactions (negative crossmatch but poor transfusion response) were unacceptably high (43% by lymphocytotoxicity, 60% by serotonin release, 76% by platelet factor 3 release, and 83% by aggregometry). We conclude that current methods of detecting isosensitization to platelet alloantigens are less satisfactory than HLA phenotyping in selecting unrelated platelet donors for an alloimmunized patient population.

Blood Platelets↗
PubMed1980

False-negative oxidase reaction as a result of medium acidification.

Acidification of the culture medium may lead to a false-negative result of the oxidase reaction. Hence, if the medium contained a carbon source or another component that is convertible to acid, a negative oxidase reaction should be considered inconclusive. In order to eliminate false-negative reactions, a reagent freshly adjusted to pH 5-7 might be used; this reagent should be checked on known oxidase-negative strains. However, we recommend that the oxidase test be performed with the normal reagent after (sub)culturing on a non-acidogenic medium.

Aeromonas↗
PubMed1992

Acetylcholinesterase histochemistry of rectal suction biopsies in the diagnosis of Hirschsprung's disease.

Rectal suction biopsy with acetylcholinesterase (AChE) histochemistry has gained increased acceptance as the means of definitely diagnosing Hirschsprung's disease (HD) as well as of excluding this diagnosis when evaluating children with low intestinal obstruction or chronic constipation since the report of Meier-Ruge et al. in 1972. But this AChE histochemical study has not been reported yet in Korea. During the 14-month period from April, 1991 through June, 1992, 37 children, aged 3 days to 17 years had rectal suction biopsies for the diagnosis or exclusion of HD. In this study, AChE histochemistry (N = 37) was compared with hematoxylin & eosin (H&E) staining of same suction biopsy specimens (N = 35) for diagnostic accuracy. The histochemical criterion used for the diagnosis of Hirschsprung's disease was that of Chow et al. (1977), i.e., the presence of many coarse discrete cholinergic fibers in the muscularis mucosae and in the immediately subjacent submucosa regardless of an infiltration of cholinergic fibers in the lamina propria. Of 13 biopsies from the patients with Hirschsprung's disease (N = 13), there were 12 positive reactions, and one false negative reaction in a neonate with total colonic aganglionosis. All biopsies from 24 unaffected children demonstrated negative reactions with no false positive reaction. In comparison, of the 35 specimens examined by H&E staining, ganglion cells were present in the submucosal Meissner's plexus only in 15 of these 24 unaffected children. In conclusion, a 97% diagnostic accuracy was achieved with AChE histochemistry compared with a 74% accuracy with H&E staining (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1992

Diagnosis of Helicobacter pylori infection in adult and pediatric patients by using Pyloriset, a rapid latex agglutination test.

Pyloriset (Orion Diagnostica, Espoo, Finland) is a rapid antibody test using latex particles coated with acid-extracted antigen of Helicobacter pylori. We evaluated its ability to predict infection in 100 adult patients and 50 pediatric patients referred for gastric endoscopy. Sixty of 65 H. pylori-infected adults were correctly identified by the test. There were 12 false-positive and 5 false-negative reactions seen. Pyloriset had a sensitivity of 92% and a specificity of 66%. The positive predictive value was 83% and the negative predictive value 82%. In contrast, sensitivity dropped to 36% in the pediatric patients and the positive predictive value was only 40%. Pyloriset could become an important alternative to other more time-consuming diagnostic tests for H. pylori-infected adult patients but is inadequate for diagnosis of pediatric H. pylori infection.

Adolescent↗
PubMed1997

Comparison of DRB sequence-based typing using different strategies.

Sequence-based typing (SBT) has become an important tool in the identification of HLA alleles. In this study a comparison was made between SBT of DRB1/3/4/5 alleles performed in two laboratories each using a different strategy for SBT. The laboratories in Utrecht and in Maastricht performed direct sequencing of PCR amplified genomic DNA from 30 selected samples. Primers and conditions for PCR amplification were different. Sequencing was either performed with T7 polymerase, using internal sequencing primers, or with cycle sequencing using an M13 tailed system. Two different automated DNA sequencers were used; the ALFexpress from Pharmacia and Applied Biosystems 373A. We concluded that nor the method of sequencing nor the sequencing machine influences typing results. However the PCR reaction used for generating template DNA is the most critical step. Different primers and different conditions can lead to false negative reactions. The fact that these false negative reactions can occur with different alleles in different combinations but not in all, implicates that extensive quality control is needed to assure correct typing results.

HLA-DR Antigens↗
PubMed1998

Clarification of HLA-B serologically ambiguous types by automated DNA sequencing.

Assignment of HLA-B types can be hampered by ambiguous reactivity of the typing sera resulting in inaccurate HLA-B assignments. In this study, 19 Korean samples exhibiting ambiguous serologic reactivities were characterized by DNA sequencing. Alleles identified from 7 samples were previously undetected in this population (B*1517, B*4101, B*4701, B*5001, and B*5106) and from 9 samples were common alleles in this population (B*4002, B*4003, B*4006, B*1501, B*1401, B*67012, and B*5401). Three samples were putative HLA-B homozygotes. Three major factors causing serologic ambiguity were identified: weak or false negative reactivity of typing sera (52.4%); cross or false positive reactivity of the sera (38.1%); and absence of information on the reaction patterns due to the lack of appropriate sera in the typing kit (e.g. B*4101 encoded molecule) or to the presence of recently characterized molecules (e.g. B*5106 encoded molecule) (9.5%). Overall, sequencing was helpful in clarifying ambiguous serologic reaction patterns improving the HLA typing for the Korean population.

Alleles↗
PubMed1980

Single tube confirmatory tests for Escherichia coli.

In a multi-laboratory trial, lauryl tryptose mannitol broth (LTMB) and minerals-modified glutamate medium with added tryptophan (MMGM + T) were compared as single tube tests for the confirmation of Escherichia coli in water; the confirmed results were also compared with the production of gas from minerals-modified glutamate medium without added tryptophan (MMGM). LTMB and MMGM + T gave similar gas and indole results with about 90% of the water samples in most of the laboratories. When compared with the 'correct' results as judged by acid and gas production from lactose peptone water and indole from tryptone water, the difference in the rate of false positive reactions between LTMB and MMGM + T was insignificant; but LTMB gave a significantly lower rate of false negative reactions than MMGM + T. Gas production from MMGM without added tryptophan gave significantly higher rates of both false positive and false negative reactions. Lauryl sulphate is therefore a suitable inhibitory surfactant for use in single tube media for the confirmation of E. coli, which can be recommended.

Bacteriological Techniques↗
PubMed1975

A new radioimmunoassay for demonstrating the antibody to hepatitis-B-surface-antigen(HBs-Ag).

A new radioimmunological system for demonstrating the antibody to hepatitis-B-surface-antigen (HBS-Ag) based on the immunoadsorption principle is described. The optimal conditions for the test are given. False-negative and false-positive results could be excluded by specificity tests on sera from 100 voluntary blood donors. The sensitivity of the system is comparable to that of other more expensive radioimmunological methods.

Antibodies↗
PubMed1982

HLA standardization and proficiency testing in the Southeastern organ Procurement Foundation.

Five years of experience with cell exchanges between laboratories comprising the Southeastern Organ Procurement Foundation (SEOPF) were analyzed in order to evaluate progress in HLA typing proficiency. The results of the analysis of 15 cell exchanges involving a total of 60 cells indicate that the average detection rate was 95% or greater for HLA-A1, 2, 3, 9, 10, 11, 28, and 29; B7, 8, 12, 13, 14, 15, 17, 27, and 40. HLA-A locus antigens were detected more often (85.8%) than B locus antigens (80.9%). False negative results were more frequent than false positive antigen assignments. Errors in antigen assignments tended to be nonrandomly distributed for certain antigens belonging to cross-reacting groups but usually were randomly distributed for well defined antigens. During the period of the study, SEOPF laboratories demonstrated improved proficiency in the identification of most HLA-A, B, and C provisional (w) specificities. The results demonstrate the benefits of interlaboratory proficiency testing and indicate that cell exchanges can be carried out successfully on a regional basis.

Cell Survival↗
PubMed1993

Polymerase chain reaction for detection of Mycobacterium leprae in nasal swab specimens.

The polymerase chain reaction based on the selective amplification of a 531-bp fragment of the gene encoding the proline-rich antigen of Mycobacterium leprae was applied to nasal swab specimens from leprosy patients, occupational contacts, and endemic and nonendemic controls. To prevent false-positive amplification, we used dUTP and uracil-DNA-glycosylase in all polymerase chain reactions. False-negative reactions were detected by using a 531-bp modified template as an internal control. Amplification products were found in 55% of untreated patients, in 19% of the occupational contacts, in 12% of endemic controls, and in none of the nonendemic controls. This study strongly suggests that not only leprosy patients but also healthy persons may carry M. leprae. We concluded that polymerase chain reaction is a reliable method to detect M. leprae in nasal specimens. The method holds promise for studying the spread and transmission of M. leprae within a population.

Contact Tracing↗
PubMed1986

Use of rapidly generated results in patient management.

The usefulness of a rapid diagnostic test in patient management depends on the sensitivity of the test, the clinical consequences of false-negative or false-positive results, the ease and cost of performance, and the timely availability of results. A test that is sensitive, specific, inexpensive, and rapid is presumed to be useful clinically. However, there has been surprisingly little effort to measure the actual impact of the results on patient care. Since antigen detection for Haemophilus influenzae type b disease has been available for more than a decade, it will be used as a model to illustrate several factors that help determine the benefits, limitations, and pitfalls of antigen detection in the management of patients with serious bacterial infections. Herein we will compare the use of antigen detection in meningitis with that in other Haemophilus influenzae type b diseases. We also will review our experience with the impact of rapid diagnosis on the treatment of bacterial meningitis. Finally, other factors that influence the usefulness of antigen detection on patient care will be explored by comparing the potential consequences of laboratory error on the management of patients with Haemophilus influenzae type b infections with that of management of other kinds of infections, such as streptococcal pharyngitis, sexually transmitted diseases, and viral respiratory infections.

Antigens, Bacterial↗
PubMed1993

Detection of anti-HIV antibodies in saliva.

It is sometimes difficult in clinical practice to identify carriers of the AIDS virus. Such identification is of unquestionable value in oral pathology, both for determining the pathogenesis of certain lesions and for assessing their significance to the patient. We evaluated several commercially available diagnostic techniques for the detection of anti-HIV antibodies in serum, and examined the feasibility of adapting such techniques to tests on saliva. The technique chosen for experimental adaptation required only slight modifications for use with this medium. We compared the results obtained in serum from intravenous drug users with a western blot assay designed to detect p24 viral protein, against the findings with a test designed to detect salivary antibodies. The likelihood of cross-reactions in saliva containing high concentrations of other antiviral antibodies was also studied. The specificity and sensitivity of the modified saliva test were 100% and 96% respectively, and no cross-reactions were observed.

AIDS Serodiagnosis↗