en Internal Medicine & Gastroenterology Internal Medicine & Gastroenterology Original Research Original Research <p><strong> Abstract</strong> </p><p> Background: At present, differentiation between exudative and transudative pleural </p><p> effusion is based solely on laboratory measures and is time-consuming. Asimple </p><p> bedside method would be of great help to differentiate between these two types of effusions. </p><p> We present a new method for this purpose assessed in 46 patients. </p><p> <strong>Methods:</strong> Standard laboratory tests and our method were tested using the same fluid </p><p> samples in 46 patients with pleural effusion. Aprincipal in physics called the capillary </p><p> tube law (h=2a/rpg) was used to compare the samples. The imbibition of the fluid </p><p> level less than 15mm signified exudate and greater than 15mm signified transudate. </p><p> <strong>Results:</strong> Our data shows that this method is 74% sensitive and 89.4% specific compared </p><p> to the standard method when analyzed statistically by the chi-square and Kappa </p><p> agreement (Cronbach’s K) tests. </p><p> <strong>Conclusion:</strong> The capillary tube test has an acceptable validity for bedside diagnosis </p><p> of exudative or transudative effusions. </p><p>  </p> exudate, transudate, pleural effusion, CTT 120 124 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-2&slc_lang=en&sid=1 Mohammad Homayouni homayouni28@yahoo.com 20031947532846001633 20031947532846001633 Yes Head of Dept. of Internal Medicine, Shohada-e- Tajrish Medical Center, Reza Hashemi 20031947532846001634 20031947532846001634 No Shohada Medical Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Ashraf Ashraf Askari 20031947532846001635 20031947532846001635 No Shemiran Health Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.