HSPA1A and infection: Using a threshold of 40 ng/ml, pleural fluid Hsp72 could help separate infection-related effusions from non-infective ones or PPE from other etiologies, although the AUC was modest (0.688 and 0.658 respectively) and was inferior to conventional biomarkers such as pH, glucose and LDH used for the differentiation of UPPE and CPPE (Table 2).