Background: Infective endocarditis (IE) is still a fatal infection with high morbidity and mortality. Successful patient outcomes depend on prompt diagnosis and effective therapy. Blood cultures are usually time consuming and sometimes echocardiography is falsely negative. Thus, a straightforward blood test may assist early diagnosis of IE. Multiple studies have revealed that procalcitonin (PCT) was highly associated with bacteremia - the main diagnostic criteria for endocarditis - in patients with fever.
Objectives: We aimed to assess the diagnostic significance of procalcitonin concentration in suspected patients of IE.
Patients and methods:  Twenty-two patients admitted to Assiut University Heart Hospital with a suspicion of IE were enrolled in a prospective study. Based on clinical, microbiological, and echocardiographic findings, Modified duke criteria were applied to the cases to confirm their diagnosis as definite, possible, or rejected IE cases before testing for procalcitonin was done. The study also included fifteen healthy volunteers for comparison with IE patients.
Results: Procalcitonin was significantly higher (P-value <0.05) in patients diagnosed as definite and possible IE than with healthy volunteers. The area under the ROC curve was 0.705. At cutoff value of 0.425 ng/ml, the procalcitonin test's sensitivity, specificity, negative predictive value, and positive predictive values were 47.6%, 93.3%, 56%, and 90.9%, respectively.
Conclusion: This study implies that procalcitonin may be a valuable supplementary diagnostic marker in IE diagnosis.  A threshold value of 0.425 ng/ml should be used for ruling out endocarditis in routine clinical practice and the diagnosis of IE can be strongly excluded below this value.