A study of Pro-brain natriuretic peptide compared with procalcitonin in critically ill patients with severe sepsis as a marker of diagnosis of sepsis

Abstract

Objective In this study we assessed the diagnostic value of Pro-brain natriuretic peptide (ProBNP) in severe sepsis and the relation of ProBNP and procalcitonin (PCT) as a biochemical marker of sepsis to cardiac dysfunction in severely septic patients. Design This was a prospective screening study. Patients and methods Twenty-four patients who were admitted to the Critical Care Medicine Department with a preliminary diagnosis of severe sepsis, defined according to the Surviving Sepsis Campaign, and 12 healthy adults as volunteers were recruited into the study. Twenty-four patients with a preliminary diagnosis of severe sepsis were divided into two groups according to echocardiography (Echo) findings. Group I included severely septic patients with normal Echo findings and group II comprised severely septic patients with abnormal Echo findings. Cultures from suspected sites of infection were obtained. Blood levels of C-reactive protein, ProBNP, and PCT were measured on admission in the case of severely septic patients. We compared ProBNP and PCT levels in severely septic patients with normal Echo findings and those with systolic and/or diastolic dysfunction and we also compared the level of ProBNP in these two groups with the control group. Results The level of ProBNP was very high, ranging from 102 to 24 244 pg/ml in all patients compared with 20–120 pg/ml in the control group. The ProBNP level was high in both groups of patients. Severely septic patients with normal or abnormal Echo findings had no significant difference regarding age, sex, vital signs, white blood count, serum creatinine, arterial blood gases, Acute Physiologic and Chronic Health Evaluation II (APACHE II) score, C-reactive protein, PCT, and ProBNP on admission. In group I, ProBNP ranged from 102 to 3776 pg/ml compared with 361 to 24 244 pg/ml in group II, with no significant difference ( P P =0.001). ProBNP was significantly higher in septic shock patients with abnormal Echo findings compared with those with normal Echo findings ( P =0.014), as well as in severely septic patients with left ventricular dysfunction (LVH) ( P =0.012). ProBNP was high with no significant difference regarding systolic and diastolic dysfunction and LVH in severely septic patients with abnormal Echo findings ( P =0.087). ProBNP level was high but there was no significant difference ( P =0.296) when correlated to culture results whether sterile or positive. The level of ProBNP in diagnosing severe sepsis in the patient group (with cutoff point>108 pg/ml as recommended by Youden’s index) had 95.83% sensitivity, 83.33% specificity, 92.0% positive predictive value (PPV), 90.91% negative predictive value (NPV), and 91.67% accuracy. To differentiate severely septic patients with normal Echo findings from those with abnormal Echo findings, ProBNP (with cutoff point>2900 pg/ml) had 41.67% sensitivity, 83.33% specificity, 71.43% PPV, and 58.82% NPV with 62.50% accuracy; PCT (with cutoff point>2 pg/ml) had 66.67% sensitivity, 50.0% specificity, 57.14% PPV, 60% NPV, and 58.33% accuracy. Therefore, ProBNP and PCT levels did not have good sensitivity or specificity in differentiating between severely septic patients with normal cardiac functions and those with abnormal cardiac functions. Conclusion ProBNP level increased with significant difference in all severely septic and septic shock patients with no impact of sex, type of organism, and site of infection. ProBNP level increased in severely septic patients with LVH, but it could not distinguish between types of ventricular dysfunction. PCT and ProBNP levels were not specific or sensitive in differentiating severely septic patients with normal cardiac function from those with abnormal cardiac function. ProBNP level was affected by renal dysfunction.