Viral Nucleic Acids in the Serum Are Dependent on Blood Sampling Site in Patients with Clinical Suspicion of Myocarditis

BACKGROUND: The meaning of viral nucleic acids in the myocardium in many cases is difficult for clinical interpretation, whereas the presence of viral nucleic acids in the serum is a marker of active infection. We determined the diagnostic value of viral nucleic acids in ventricular serum and peripheral serum samples in comparison with endomyocardial biopsy (EMB) specimens in patients with clinically suspected myocarditis. METHODS: The viral nucleic acid evaluation was performed in serum samples and EMB specimens by real-time PCR in 70 patients (age: 47 ± 16 years). The biopsy specimens were examined by histo- and immunohistochemistry to detect inflammatory response. RESULTS: The viral nucleic acids were detected in ventricular and peripheral serum, and EMB samples of 10 (14%), 14 (20%), and 32 (46%) patients, respectively. Notably, viral nucleic acids of the same virus as in the EMB sample were present more often in ventricular than in peripheral serum (60 vs. 7%, p = 0.01). A significant concurrence was observed between the positive and the negative results of viral nucleic acids present in EMB and ventricular serum (p = 0.0001). CONCLUSIONS: The detection of the same viral nucleic acid type in the myocardium and in ventricular serum being significantly more frequent than in the peripheral serum may suggest that the site of the blood collection is important for more precise and reliable confirmation of the active viral replication in the heart.