Letters |
April 2012 Comparing APTT reagents There is an obvious mistake in Fig. 2 (Cumulative summation of differences method for comparing APTT reagents) and the interpretation of the CAP requirements for comparing APTT lots (Q&A, February 2012). One cannot compare two lots over a nine-year period using the statistics implied in this figure. You can compare two lots within a year or less using 10–30 individual paired-comparison type statistics, not means on a yearly basis. The paired comparison analysis does compare the mean differences between the individual specimens and gives a significance related to the difference. I cannot determine what clinical significance can be derived from the analysis shown in Fig 2. of this report. If there is one, please let me know. Leon Zuckerman, PhD • Russell A. Higgins, MD, of the University of Texas Health Science Center at San Antonio and vice chair of the CAP Coag-ulation Resource Committee, and Sandra C. Hollensead, MD, of the University of Louis-ville (Ky.) Hospital and a member of the CAP committee, reply: Dr. Zuckerman has a valid concern about the statistical model. The cumsum model has not been evaluated formally. To explain the method a bit further: Comparison data (APTTs on heparinized patients) are plotted with the old APTT reagent on the x-axis and the new reagent on the y-axis. Visual or regression analysis is performed to compare data and identify discrepant and outlier results. The data for each APTT reagent are summed and the mean and standard deviation determined. The difference between the means of the new and old APTT reagents are then recorded. In the following year (or at the next APTT reagent change), the comparison data are again determined, and the difference of the means is added to the difference between the old and new reagents from the year before. In this way, drift in sensitivity of the reagent caused by multiple changes over time can be detected and controlled. If the cumulative mean is greater than seven seconds in any year of comparison data, the reagent is rejected, and another reagent performing more closely with the laboratory’s past reagents may be chosen. Although not a formal component of the method at this time, an SD comparison year to year could be a valuable piece of information in identifying reagents with high variability. Despite great effort on the part of laboratories, physicians may be reluctant to change practices. Performance measures The Cleveland Clinic Measures Consortium was established in 2010 with the goal of developing evidence-based quality and performance measures associated with the pre- and postanalytic stages of laboratory testing. In cooperation with the Centers for Disease Control and Prevention and a panel of national experts in laboratory testing, the consortium has identified several areas as high priorities. We invite comments from the professional community about the relative importance of the following proposed parameters, as well as opinions regarding which quality indicators should receive priority for study. We invite recommendations for parameters not listed here. The parameters that are ultimately given the highest priority will be studied to establish essential quality and performance measures. Please address correspondence to the e-mail address at the end of this letter. The public comment period ends May 15. Here are the high-priority areas: Incorrect patient identification. Assessment of the baseline frequency of specimens with incorrect patient identification and the impact of incorrect patient identification (re-acquisitions, continued therapy without the benefit of the laboratory test, for example). Unnecessary same-day duplicate orders. The frequency of unnecessary same-day duplicate orders and the financial and clinical impact of stopping such orders. Improper handling of abnormal test results. How and when abnormal test results were acknowledged in the medical record, to determine if they received followup, to assess the impact of the failure to address these results, and to determine if missed laboratory results were likely due to interface issues. Appropriate use of coagulation testing/hypercoagulation panel. This includes:
Appropriate use of HbA1c. This includes:
Appropriate use of constitutional molecular genetic tests. This includes:
Testing for C. difficile by PCR. This includes:
Lipid testing in association with stroke. This includes:
Gary W. Procop, MD, MS Send letters to Editor, CAP TODAY, 325 Waukegan Road, Northfield, IL 60093. Fax: 847-832-8873; srice@cap.org. |