The IL-6 value in the differential diagnosis of the exudative pleural effusion

Hippokratia 2001, 5(4):172-175

A Christopoulos, Ath Notopoulos, G Liaros, Ir Katsarou, P Andricacos, E Phegou, O Drakoulogona, L Panteli, E Mendrinou


Interleukin 6 (IL-6) is locally produced at the sites of inflammation of the pleural space. It is also known that some malignant cells produce IL-6. Pleural IL-6 leaks to systemic circulation and causes systemic effects. In this study we measured IL-6 in serum/pleural fluid paired samples in various groups of patients with exudative pleural effusions. In the serum were detected significantly higher IL-6 values in patients with parapneumonic effusions (n=32, mv 12.3±6.lU/ml) in comparison to tbc effusions n=23 mv 4±3 U/ml, (p=0.00464) as well as to malignant effusions n=20, mv 5.4±3.9U/ml (p=0.02). In the pleural fluid the tbc effusions presented with significantly higher IL-6 values (mv 498±276 U/ml), in comparison to malignant effusions (mv 42+56.2 U/ml), (p=0.0046) as well as to parapneumonic effusions (mv 244±192 U/ml), (p=0.01). The serum/pleural IL-6 ratio, was: 1) tbc effusions 0.02, 3) malignant effusions >0.1. Ninety six per cent of the malignant effusions were presented with a pleural fluid’s IL-6 value < 100 U/ml, whereas all the empyemas and the tbc effusions were presented with a value > 100 U/ml. These results suggest that the serum/pleural fluid’s IL-6 ratio (IL-6 criterium) together with pleural fluid’s IL-6 values can lead to quick differential diagnosis of the exudative pleural effusion, which will be confirmed later with the traditional practice methods.