3 test rule

Q: Three-test rule is used to diagnose which disease?

Answer: Pleural effusion

Although Light's criteria is considered a standard to distinguish transudative and exudative pleural effusion. There are equally reliable and easy to apply tests available like Two-test and three test rules.  The fluid is most probably exudative if:

 Two-test rule 

•  Pleural fluid cholesterol > 45 mg/dL 
•  Pleural fluid LDH > 0.45 times the upper limit of the normal serum LDH 

Three-test rule 

•  Pleural fluid protein > 2.9 g/dL 
•  Pleural fluid cholesterol > 45 mg/dL 
•  Pleural fluid LDH > 0.45 times the upper limit of the normal serum LDH

#pulmonary

References:

1. Paramothayan NS, Barron J. New criteria for the differentiation between transudates and exudates. J Clin Pathol. 2002;55(1):69–71. doi:10.1136/jcp.55.1.69

2. Na MJ. Diagnostic tools of pleural effusion. Tuberc Respir Dis (Seoul). 2014;76(5):199–210. doi:10.4046/trd.2014.76.5.199

3. Romero S, Candela A, Martin C, et al. Evaluation of different criteria for the separation of pleural transudates from exudates. Chest 1993;104:399–404. 

4. Burgess LJ, Maritz FJ, Taljaard JJF. Comparative analysis of the biochemical parameters used to distinguish between pleural transudates and exudates. Chest 1995;107:1604–9. 

5. Gonlugur U, Gonlugur TE. The distinction between transudates and exudates. J Biomed Sci 2005; 12:985. 

6. Kummerfeldt CE, Chiuzan CC, Huggins JT, et al. Improving the predictive accuracy of identifying exudative effusions. Chest 2014; 145:586.