scholarly journals Supplementary Testing Is Not Required in the cobas 4800 CT/NG Test for Neisseria gonorrhoeae Weak-Positive Urogenital Samples

2014 ◽  
Vol 53 (1) ◽  
pp. 327-328 ◽  
Author(s):  
Collette Bromhead ◽  
Nadika Liyanarachchy ◽  
Julia Mayes ◽  
Arlo Upton ◽  
Michelle Balm
Keyword(s):  
Nucleic Acid ◽  
Neisseria Gonorrhoeae ◽  
Nucleic Acid Amplification Test ◽  
Pretest Probability ◽  
Nucleic Acid Amplification ◽  
Test Results ◽  
Content Type

Weak-positiveNeisseria gonorrhoeaenucleic acid amplification test results are difficult to interpret. We show that the frequency of unconfirmedN. gonorrhoeaeresults from the cobas 4800 test rises exponentially after 38.0 cycles, where the likelihood of an unconfirmed result exceeds 29%. Supplementary testing of such samples should be avoided; instead, treatment should be based on clinical pretest probability.

scholarly journals Nucleic Acid Amplification Test Quantitation as Predictor of Toxin Presence in Clostridium difficile Infection

2017 ◽  
Vol 56 (3) ◽  
Author(s):  
M. J. T. Crobach ◽  
N. Duszenko ◽  
E. M. Terveer ◽  
C. M. Verduin ◽  
E. J. Kuijper
Keyword(s):  
Nucleic Acid ◽  
Clostridium Difficile ◽  
Characteristic Curve ◽  
Nucleic Acid Amplification Test ◽  
Nucleic Acid Amplification ◽  
Toxin A ◽  
Toxin B ◽  
Content Type ◽  
Quantitative Results ◽  
Testing Algorithm

ABSTRACT Multistep algorithmic testing in which a sensitive nucleic acid amplification test (NAAT) is followed by a specific toxin A and toxin B enzyme immunoassay (EIA) is among the most accurate methods for Clostridium difficile infection (CDI) diagnosis. The obvious shortcoming of this approach is that multiple tests must be performed to establish a CDI diagnosis, which may delay treatment. Therefore, we sought to determine whether a preliminary diagnosis could be made on the basis of the quantitative results of the first test in algorithmic testing, which provide a measure of organism burden. To do so, we retrospectively analyzed two large collections of samples ( n = 2,669 and n = 1,718) that were submitted to the laboratories of two Dutch hospitals for CDI testing. Both hospitals apply a two-step testing algorithm in which a NAAT is followed by a toxin A/B EIA. Of all samples, 208 and 113 samples, respectively, tested positive by NAAT. Among these NAAT-positive samples, significantly lower mean quantification cycle ( C q ) values were found for patients whose stool eventually tested positive for toxin, compared with patients who tested negative for toxin (mean C q values of 24.4 versus 30.4 and 26.8 versus 32.2; P < 0.001 for both cohorts). Receiver operating characteristic curve analysis was performed to investigate the ability of C q values to predict toxin status and yielded areas under the curve of 0.826 and 0.854. Using the optimal C q cutoff values, prediction of the eventual toxin A/B EIA results was accurate for 78.9% and 80.5% of samples, respectively. In conclusion, C q values can serve as predictors of toxin status but, due to the suboptimal correlation between the two tests, additional toxin testing is still needed.

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