Question

Why are nucleic acid tests more likely to return a false positive than culture based testing methods?

Answer 1

Ans-  Nucleic acid amplification testing involves the detection of pathogen-specific DNA or RNA sequences in patient samples. There are a number of different methods – PCR is one type. Compared to traditional methods, nucleic acid amplification testing offers improved turnaround times and markedly enhanced sensitivity. These techniques are easily adapted to high-throughput testing and can allow multiple pathogen identification within a single test. Nucleic acid amplification testing is currently revolutionising areas where traditional microbiological methods have been complex, costly and time consuming, such as the diagnosis of faecal pathogens.

Nucleic acid tests more likely to return a false positive, beacuse loss or changes to the target nucleic acid sequence through mutation can lead to false negative results. Furthermore, because of their extreme sensitivity, contamination can lead to false positives.

Additionally, Problems with assay specificity can potentially lead to false positives. Early nucleic acid amplification tests for N. gonorrhoeae resulted in significant rates of false positives due to cross reactions with commensal Neisseria species. Most testing platforms include both C. trachomatis and N. gonorrhoeae in multiplex assays. Laboratories report both results despite the generally lower prevalence of N. gonorrhoeae. To reduce false positive results, laboratories invariably confirm initial positive N. gonorrhoeae results using a second independent assay. This increases the positive predictive value of the reported positive result.