Background Cell-free DNA is observed to be more in exudative pleural effusions. Based on this fact development of a clinical chemistry test for classification of pleural effusion will require DNA extraction followed by PCR amplification and electrophoresis. These procedures may not be cost effective for the purpose for classification of pleural effusion as already established parameters are popular for the purpose which can be estimated by comparatively low cost colorimetric procedures. Therefore development of a simple colorimetric test for the classification of pleural fluid based on nucleic acid identification test can be attempted. The aim of this work is to develop such colorimetric test for classification of pleural effusion using only pleural fluid sample. Methods Cell pellet is obtained from 5 ml pleural fluid which is lysed and subjected to DNA extraction, followed by identification under UV-transilluminator after electrophoresis and orcinol and diphenylamine reaction. Result Exudates show extractable DNA from 5 ml biofluid (n = 52) which are not observed from transudate (n = 32). Orcinol reaction is significantly positive in exudates (n = 52) compared to the transudates (n = 32). Diphenylamine test cannot differentiate exudate from transudate. Conclusion Orcinol reaction of cell lysate obtained from pleural fluid can classify pleural fluid sample into exudate or transudate.
