Imazio M, Biondo A, Ricci D, et al. - Given that the initial evaluation of pericardial fluid (PF) is commonly done via biochemical analysis of PF, and Light’s traditional criteria are usually used for interpreting results for the differential diagnosis of transudates vs exudates, researchers performed this cohort study to assess the normal composition of PF in candidates for cardiac surgery. Prior pericardial disease or cardiac surgery, prior myocardial infarction within 3 months, systemic disease (eg, systemic inflammatory diseases, uremia) or drug with the potentiality to affect the pericardium were all included in the exclusion criteria. This study included 50 patients (mean age was 67 years, 29 males). In blood and PF, similar levels of small molecules were detected. Compared with corresponding plasma levels, total proteins in PF was, on average, 0.5 times lower. On average, 1.06 times higher level of pericardial lactate dehydrogenase was detected as compared with plasma level. Moreover, more concentrated mononuclear cells were detected in PF as compared with plasma. In candidates for cardiac surgery, normal PFs were misclassified as exudates by traditional Light’s criteria, and therefore, were suggested as futile for the biochemical examination of PF in clinical practice.