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J W Ross

Publications and source records attributed to J W Ross.

At least 55 records · Page 3Linked to original sources
PubMed1993

Analytical goals developed from the inherent error of medical tests.

Biological variation is inherent in all medical tests and is a major source of error in clinical test interpretation. We use inherent test error due to biological variability as the touchstone by which to validate the clinical acceptability of analytical goals. Analytical goals should consist of sets of complementary limits for total error, bias, and imprecision and a medical usefulness criterion (MUC) to ensure that the total error goal is met with stated certainty. We propose analytical goals that are limits for the total error of a measurement system, the joint capability of the process control procedures and the measurement process. Thus, the goals are the allowable analytical error for proficiency evaluation, internal process control, and the total error budget for design of method performance characteristics. We define MUC as the allowable maximum proportion of test diagnostic efficiency lost due to analytical error near medical decision points. MUCs < 0.03 are not routinely clinically useful; MUCs > 0.08 allow method performance characteristics that are undesirable for general clinical use. Using MUC = 0.05 and recommendations that imprecision not exceed one-half of the biological CV, we propose that fixed bias should not exceed one-fourth to one-third of the intraindividual biological CV of the analyte and that total analytical error should not exceed 1.25 to 1.40 times the biological CV. Modification of these analytical goals may arise for reasons of documented clinical practice or process stability. Our model quantifies in medical utility terms the results of such modifications.

Bias↗
PubMed1993

Matrix effects on proficiency testing materials. Impact on accuracy of cholesterol measurement in laboratories in the nation's largest hospital system.

The objective of this collaborative study with the Department of Veterans Affairs (VA), College of American Pathologists (CAP), and the Centers for Disease Control and Prevention (CDC) was to quantitate the matrix-induced biases of cholesterol measurements on the CAP Comprehensive Chemistry Surveys materials used in proficiency testing (PT). A total of 174 VA Medical Centers outpatient clinics and clinical laboratories participate in the VA-CDC National Cholesterol Standardization and Certification Program. This study was conducted in 112 VA laboratories that have been standardized for measuring cholesterol accurately (within +/- 3.0% of the CDC reference-method values) using fresh, unfrozen, unadulterated human serum samples. Fresh serum samples and 1990 CAP Surveys materials were sent by overnight mail, and the laboratories were asked to analyze them simultaneously in triplicate in a single analytic batch run. The results showed significant matrix-effect biases with the CAP Surveys materials with six of the eight major peer groups, despite the fact that accuracy of cholesterol measurements was maintained with fresh serum samples. The magnitude and direction (positive or negative) of the matrix-effect biases were instrument, reagent, and method specific using the following peer groups: du Pont Dimension (-8.9%); Beckman CX4, CX5, and CX7 (-5.5%); Kodak Ektachem 400, 500, and 700 (+4.4%); Instrumentation Laboratory Monarch (-3.1%); Baxter Paramax (-2.4%); Technicon SMAC and RA (+1.3%); Hitachi/BMD 704 through 747 (+0.4%); and Abbott Spectrum (-0.3%). The CAP PT materials used currently do not behave in a manner identical to fresh human serum when measuring cholesterol on many, but not all, analytic systems. The observed biases due to "matrix effects" with PT materials will cause incorrect conclusions about the accuracy of many laboratory procedures performed on fresh patient specimens. This matrix-effect phenomenon will severely hamper interlaboratory accuracy transfer, standardization efforts, and monitoring performance of a laboratory's testing accuracy with the use of the current survey materials used in PT programs. Collaborative efforts are needed to (1) improve PT fluids to analytically behave more like fresh, human serum; (2) improve instrument design and reagent formulation; and (3) select methods and methodologic parameters that are more "robust" and less sensitive to the exact character of processed calibrators, quality control, and PT materials.

Bias↗
PubMed1993

Matrix effects and the accuracy of cholesterol analysis.

We found evidence of bias due to matrix effect in 70% of 37 instrument/reagent-specific systems analyzing the total cholesterol content of a lyophilized proficiency testing material. We used a computational method to remove bias due to matrix effect from the proficiency testing database. After correction for matrix effect bias and when compared with the reference method, 92% to 93% of results for three lyophilized proficiency testing samples analyzed in 1989 and 1990 met the 1992 National Cholesterol Education Program total error goal of 8.9%, and 94% to 95% met the Clinical Laboratory Improvement Amendments of 1988 (CLIA '88) goal of 10%. However, compared with the definitive method for total cholesterol, the calibration bias of 41% of 37 peer groups exceeded the 1992 National Cholesterol Education Program goal for bias of 3%. Because the calibration bias of the method is incorporated into the peer group mean, use of peer group means as target values to assess result acceptability hinders advancement of the state of the art in interlaboratory comparability and the clinical effectiveness of laboratory testing. The prevalence of matrix effects has prevented successful application of accuracy-based evaluation of cholesterol test proficiency. The establishment of predictable recovery, preferably complete recovery, of cholesterol from reference materials is an important priority for cholesterol test methods. However, adjustment of proficiency testing results to remove the average bias due to matrix effects can help assess the actual state of the art in cholesterol test accuracy.

Bias↗
PubMed1991

Elder abuse.

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Aged↗
PubMed1989

Trismus and multifocal soft tissue ossification. A presentation of fibrodysplasia ossificans progressiva?

A 21-year-old female patient presented with trismus, initially diagnosed as related to pericoronitis. Computed tomography demonstrated heterotopic soft tissue ossification involving both medial pterygoids which was later followed by similar features in the submandibular muscles and right quadriceps. A variant of fibrodysplasia ossificans progressiva was considered the likeliest diagnosis. The computed tomographic features of the condition and the importance of early diagnosis are stressed.

Adult↗