Patient Self Testing Meters are Highly Accurate

When used by trained patients, patient self testing meters provide up to 97% correlation to results obtained by a lab or at the point of care.

Researchers conducted a study to evaluate the performance of the CoaguChek XS System – specifically in terms of accuracy and precision – compared to standard traditional laboratory methods. Prothrombin Time test results were obtained from CoaguChek XS monitors from three external sites, using both capillary and venous whole blood.


  • Precision: The precision of a system is its ability to replicate measurements to give similar results. Whole blood precision was analyzed separately for normal donors (those patients not on warfarin) and donors taking warfarin. The study measured precision for both capillary and venous whole blood. Acceptable results for precision were obtained.
  • Accuracy: A correlation coefficient is 0.976 for the results of the CoaguChek XS System vs. capillary data (i.e., comparable to Point of Care Testing). A correlation coefficient is 0.980 for the results of the CoaguChek XS System vs venous blood data (i.e., comparable to Lab testing).


Prothrombin Time testing is not standardized across systems – whether they are lab instruments or portable point-of-care monitors. There is no defined "gold" standard for acceptable performance. The coefficients of variation presented for precision of whole blood duplicates indicate that the precision of the CoaguChek XS monitor for both capillary and venous whole blood samples is very good. Regression statistics yielded correlation coefficients of 0.97 or greater for all comparisons.

Source: White Paper by Jennifer L. Fuller, MS, CCRA, and Earl Miller, MS, of Roche Diagnostics Corporation.