Since 1988, the College of American Pathologists has been offering materials for calibration verification coupled with the surveys for linearity, called the linearity (LN) surveys.
To determine whether successful completion of the College of American Pathologists LN surveys provides a benefit in terms of improved proficiency testing (PT) performance.
In this study, we used information from LN surveys LN1/2, LN3, and LN5 and from the PT surveys C, Z, and K administered and analyzed in the year 2000. For the PT data, we calculated 4 measures of performance: passing PT, results exceeding 2 SDs, sum of absolute SD intervals, and the absolute sum of SD intervals. For the LN data, we classified laboratories as participants versus nonparticipants in LN surveys and by whether or not LN survey performance was successful.
LN enrollees had fewer unacceptable PT results than did nonenrollees. Additionally, for many analytes there was a significant positive association between LN performance and PT performance.
For most analytes studied, there was strong evidence linking performance on PT surveys with performance on LN surveys. Eight of 13 analyses (62%) demonstrated improved performance with successful calibration verification.