Background and Aim: In cases under heparin therapy, frequent blood samples must be taken for coagulation tests. Therefore, samples from saline lock can be a useful means to decrease the pain of taking frequent blood samples. The purpose of this study was to find the effect of this method on the validity of coagulation tests results.

  Materials and Methods: In this case-control study a convenience sample of 63 cardiac patients participated. The blood sample taken from saline lock was accounted as the case and that taken from the opposite arm was the control sample. In order to obtain blood from saline lock, a tourniquet was applied proximal to the saline lock devices, after the first 0.5 ml of blood withdrawn was discarded and the next 5 ml blood sample was gathered for coagulation tests analyses. Simultaneously, a venipuncture 5 ml sample drawn from the opposite arm was taken as the control. Both blood samples were analyzed for coagulation tests. Results were analyzed by means of SPSS version 11.5 and paired T-test.

  Results: Among the cases under study 53.96% were men. The most common reason of admission was unstable angina (46.03%). There were no significant differences in mean coagulation values in the blood samples obtained through venipunctures and those drawn from saline locks (P>0.05).

  Conclusion: According to the results of this study, vein saline lock catheter sampling is a reliable and proper method for coagulation tests and can be a good alternative method in those patients who need repeated blood sampling.