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J R Hackney

Publications and source records attributed to J R Hackney.

6 recordsLinked to original sources
PubMed1993

A systems approach to assure optimal proficiency testing in the hematology laboratory.

Although CLIA 88 has probably caused the laboratorian to place inordinate emphasis on proficiency testing, we believe that it will ultimately improve clinical laboratory practice. Due to the increased numbers of challenges within a mailing, the laboratorian has a greater ability to gauge magnitudes and types of any existing error. These magnitudes can be compared with previously established limits to determine the need for corrective action. Laboratories are encouraged to devise a system to guarantee accurate preanalytic, analytic, and postanalytic PT processing and reporting. Due to the relatively low imprecisions of today's hematology analyzers compared with the HCFA limits, most hematology laboratories should focus their attention on measures of and factors affecting long-term control and calibration. More attention should be paid to moving averages of indices and the analytic performance in regional or manufacturer control pools.

Calibration↗
PubMed1993

The detection of problem analytes in a single proficiency test challenge in the absence of the Health Care Financing Administration rule violations.

The Clinical Laboratory Improvement Act of 1988 (CLIA 88) has dramatically changed proficiency testing (PT) practices having mandated (1) satisfactory PT for certain analytes as a condition of laboratory operation, (2) fixed PT limits for many of these "regulated" analytes, and (3) an increased number of PT specimens (n = 5) for each testing cycle. For many of these analytes, the fixed limits are much broader than the previously employed Standard Deviation Index (SDI) criteria. Paradoxically, there may be less incentive to identify and evaluate analytically significant outliers to improve the analytical process. Previously described "control rules" to evaluate these PT results are unworkable as they consider only two or three results. We used Monte Carlo simulations of Kodak Ektachem analyzers participating in PT to determine optimal control rules for the identification of PT results that are inconsistent with those from other laboratories using the same methods. The analysis of three representative analytes, potassium, creatine kinase, and iron was simulated with varying intrainstrument and interinstrument standard deviations (si and sg, respectively) obtained from the College of American Pathologists (Northfield, Ill) Quality Assurance Services data and Proficiency Test data, respectively. Analytical errors were simulated in each of the analytes and evaluated in terms of multiples of the interlaboratory SDI. Simple control rules for detecting systematic and random error were evaluated with power function graphs, graphs of probability of error detected vs magnitude of error. Based on the simulation results, we recommend screening all analytes for the occurrence of two or more observations exceeding the same +/- 1 SDI limit. For any analyte satisfying this condition, the mean of the observations should be calculated. For analytes with sg/si ratios between 1.0 and 1.5, a significant systematic error is signaled by the mean exceeding 1.0 SDI. Significant random error is signaled by one observation exceeding the +/- 3-SDI limit or the range of the observations exceeding 4 SDIs. For analytes with higher sg/si, significant systematic or random error is signaled by violation of the screening rule (having at least two observations exceeding the same +/- 1 SDI limit). Random error can also be signaled by one observation exceeding the +/- 1.5-SDI limit or the range of the observations exceeding 3 SDIs. We present a practical approach to the workup of apparent PT errors.

Bias↗
PubMed1990

The use of retained patient specimens for haematology quality control.

Patient blood specimens constitute ideal quality control material in many respects. Although stability is a problem, patient specimens are sufficiently stable to allow their use in the control of short-term systematic error. The principal challenges involve the design of a system which combines excellent performance characteristics (probability of error detection and probability of false rejection) with a minimum of extra work. In the past, guidelines have been presented for an optimized quality control program using retained patient specimens in haematology. These guidelines call for the use of three retained specimens initially analysed only once, with subsequent analyses judged 'out of control' if they deviate from the initial result by a prescribed multiple of the long-term standard deviation. In practice, this system may result in a relatively high probability of false rejection of data (Pfr) due to inadequately established control ranges. Also, the maintenance of three retained patient specimens may be an excessive burden on small laboratories. We present data on the optimization of a quality control program using one retained specimen that is appropriate for use by smaller laboratories. The control rules and the number of initial analyses are adjusted to yield the highest possible probability of error detection (Ped while maintaining a low Pfr and a low additional workload. In addition, we present data concerning the control of satellite instruments by sharing patient specimens between the satellite instrument and a 'reference' instrument.

Computer Simulation↗
PubMed1986

Need for improved instrument and kit evaluations.

A review of method comparison studies published in the American Journal of Clinical Pathology indicates that hematology evaluations are less rigorous than their chemistry counterparts and rely heavily on the correlation coefficient. While clinical chemistry evaluations depend more on linear regression, they tend to omit relevant, lesser-known statistics, such as the standard error of the estimate. The authors reiterate guidelines for the collection and statistical analysis of method comparison data and recommend that both hematology and chemistry evaluations be improved.

Blood Coagulation Tests↗