A comparison of the Murphy-Pattee and the Seligson methods for serum thyroxine

We compared two methods for serum thyroxine measurement by competitive protein binding - the Murphy and Pattee and the Seligson and Seligson methods. We found the Seligson and Seligson method, which requires less sample volume and analysis time, to be the method of choice on the basis of sensitivity, extraction efficiency, precision, and accuracy. Standard plots of time/10,000 counts versus thyroxine concentration are linear to 20 ug/dl, extraction efficiency is 99.6 per cent, within-day S.D. plus or minus 0.28 ug/dl, and 98.3 per cent of added thyroxine is recovered in the Seligson and Seligson method. The Seligson and Seligson method is superior to the Murphy and Pattee method with respect to all these parameters. The methods were also compared with correlation and normal value studies.