In patients presenting with lymphocytic exudative pleural effusion, a simple marker of raised pleural fluid CRP level may be helpful in discriminating between TBP and MPE.

The prevalence of p-ANCA in Thai patients with ulcerative colitis (39.4%) is lower than that in the Western population. Although the prevalence of p-ANCA is low in the Thai population, it should serve as a useful tool in diagnosing ulcerative colitis in this part of the world where the disease is uncommon and difficult to diagnose. The negativity of p-ANCA in almost all first-degree relatives of Thai ulcerative colitis patients should be further elucidated.

We appreciate the useful comments on our article (Respirology vol 9 issue 1) 1 by Dr Garcia-Pachon and colleagues. We agree that the exclusion of the nonspecific pleuritis group makes the application of this test in clinical practice limited, as stated in the 'Discussion' section. But in reality, up to 20% of patients evaluated for an aetiological cause of their pleural effusion are initially undiagnosed. 2 The additional data from Garcia-Pachon and colleagues demonstrated comparable results to our study, with the value of pleural fluid C-reactive protein > 30 mg/L for diagnosing tuberculous pleuritis (sensitivity, 100% vs 72%; specificity, 71% vs 93%). However, to apply this test in a different place, especially a different study population, the prevalence of the target disease or disorder must be known. 3 REFERENCES1 Chierakul N, Kanitsap A, Chaiprasert A, Viriyataveekul R.A simple C-reactive protein measurement for the differentiation between tuberculous and malignant pleural effusion.