PubMed · 4905921
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S H Ferguson, E C Prather, C L Nayfield. 1970. Clinically significant mycobacteria.. https://doi.org/10.1097/00007611-197003000-00017
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We prospectively evaluated 639 sequential clinical isolates of alpha-hemolytic gram-positive cocci as possible Streptococcus pneumoniae. On the basis of results of tests for optochin susceptibility, tube bile solubility, and the quellung reaction, 74 strains (11.6%) were categorized as unequivocal pneumococci (optochin positive, tube bile solubility positive, quellung reaction positive). Among 450 optochin- and tube bile solubility-negative organisms, a subset of 56 strains was tested for quellung reaction (all negative); these isolates were categorized as unequivocal nonpneumococci. A final 115 organisms with an inconsistent or discordant combination of susceptibility to optochin, tube bile solubility, and quellung reaction were categorized as equivocal strains. With the unequivocal isolates, a commercial molecular probe for S pneumoniae (AccuProbe; Gen-Probe, San Diego, Calif) showed 100% sensitivity (74/74) and 100% specificity (56/56). Among the 115 equivocal strains, however, 33 (28.7%) reacted with the AccuProbe, whereas only 3 (2.6%) showed a capsule that reacted in the quellung test. A subset of the equivocal strains identified in this group of primarily respiratory isolates may have been S pneumoniae that only partially expressed their classic phenotype of optochin susceptibility and bile solubility and only rarely expressed capsular antigens. A practical, cost-sparing algorithm is proposed to facilitate the routine clinical identification of S pneumoniae.
OBJECTIVES: Several methods are used to detect Helicobacter pylori (HP) infection. However, few reports have evaluated the accuracy of each method and compared the grade of HP infection with the severity of histological changes. HP infection was evaluated semiquantitatively in relation to the severity of gastritis, and the sensitivity, specificity, and accuracy of several methods to detect HP infection were compared. METHODS: Biopsy specimens, obtained from a total of 64 patients who underwent endoscopy for evaluation of gastroduodenal diseases, were studied using a rapid urease test, culture, and histological assessment. An immunohistochemical method was used as the gold standard and graded according to the number of individual bacteria seen, as follows: 0 = 0; 1+ = <10; 2+ = 10-29; 3+ = 30-99; 4+ = >100. The severity of gastritis was evaluated histologically in each specimen and compared with the grade of HP infection. RESULTS: The rapid urease test had a sensitivity of 53%, specificity of 100%, and accuracy of 73%. The culture method had a sensitivity of 75%, specificity of 100%, and accuracy of 86%. Sensitivities of the rapid urease test and the culture method decreased in a positive correlation with the decrease in total number of HP bacteria counted. Using the rapid urease test, sensitivity was <30% when the grade of HP infection was < or =2+, whereas 100% sensitivity was obtained when the grade of HP infection was 4+. On the other hand, sensitivity of the culture method remained between 80% and 90% when HP infection was > or =2+. The severity of gastritis determined with Rauws scores increased in a positive correlation with the grade of HP infection as evaluated by immunohistochemical stain. CONCLUSIONS: The rapid urease test and culture of HP may result in false-negative tests for a mild infection, although they had high sensitivity and specificity for moderate to severe infection. Immunohistochemical stain provides a reliable semiquantitative diagnosis of HP infection and a positive correlation with histological changes. Clinicians should be aware of the characteristics of each method to detect HP infection and select the appropriate one(s) for their purposes.
PURPOSE: To provide a qualitative evaluation of the predictive value of the laboratory diagnosis of Lyme disease and to use the resultant data to formulate guidelines for clinical diagnosis. DATA SOURCES: A MEDLINE search of English-language articles or articles with English-language abstracts published from 1982 to 1996. DATA EXTRACTION: Sensitivity, specificity, and likelihood ratios were calculated, and a random-effects model was used to combine the proportions from the eligible studies. Prespecified criteria were used to determine which studies were eligible for analysis. DATA SYNTHESIS: Laboratory testing in general is not clinically useful if the pretest probability of Lyme disease is less than 0.20 or greater than 0.80. When the pretest probability is 0.20 to 0.80, sequential testing with enzyme-linked immunosorbent assay and Western blot is the most accurate method for ruling in or ruling out the possibility of Lyme disease. CONCLUSIONS: Laboratory testing is recommended only in patients whose pretest probability of Lyme disease is 0.20 to 0.80. If the pretest probability is less than 0.20, testing will result in more false-positive results than true-positive results; a negative test result in this situation effectively rules out the disease.