Scripties UMCG - Rijksuniversiteit Groningen
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Design and evaluation of a new lytA-based qPCR in patients with acute exacerbation of chronic obstructive pulmonary disease and community acquired pneumonia

(2018) Kamies, B.A.

In acute exacerbation of COPD (AECOPD) and community acquired pneumonia (CAP) there is a need for improved diagnostic precision to monitor protection by pneumococcal vaccination, to help design empirical treatment regimens, and to monitor drug susceptibility. In both conditions the tests for S. pneumoniae are suboptimal. Recent studies reveal enhanced diagnostic gain of quantitative PCR. Clearly, qPCR testing has its challenges. Research findings and opinions are divergent in respect to sensitivity and specificity. The first aim of this study was to improve the qPCR primer design. Further, this study investigated the diagnostic yield in CAP and AECOPD patients with a specific lytA qPCR for S. pneumoniae.
At first, improvement of the lytA qPCR design was elaborated and tested based on different pneumococcal strains and non-pneumococcal streptococci. Subsequently 226 oropharyngeal swabs and 188 nasopharyngeal swabs were tested with the original and new lytA qPCR design. These swabs were taken from CAP and AECOPD patients. The results were compared to current pneumococcal diagnostics (sputum culture, blood culture and urine antigen test).
With the new lytA qPCR, 57 (25%) of the CAP patients tested qPCR-positive, among whom 25 new patients undetected by standard tests. 15(8%) of the AECOPD patients tested qPCR positive. In the CAP group, the sensitivity was 54% and specificity was 84%. In subgroup analysis with only the cases where all three standard tests were performed the sensitivity was 67%. Pre-treatment with antibiotics decreased the number of PCR-positive swabs significantly with 59%. In both the CAP and AECOPD group, the patients with a positive qPCR test had a significantly higher C-reactive protein (CRP) value than those with a negative qPCR outcome.
The new lytA design led to a more specific pneumococcal PCR and the results in clinical samples agree with previous investigations. Both the advantage of qPCR technique and the downside of the harvesting site became clear in the results.

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