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G S Cembrowski

Publications and source records attributed to G S Cembrowski.

At least 37 records · Page 2Linked to original sources
PubMed1993

Physician goals and laboratory test turnaround times. A College of American Pathologists Q-Probes study of 2763 clinicians and 722 institutions.

Laboratory test turnaround times (TATs) for emergency department patients were studied in 722 institutions using Q-Probes, a quality improvement program of the College of American Pathologists. The medians of the TATs required by 2763 clinicians were 10 minutes for PO2, 20 minutes for hemoglobin, and 30 minutes for potassium and glucose measurements. Surgeons had the shortest TAT requirements for hemoglobin, potassium, and glucose measurements, whereas emergency department physicians had the shortest requirements for PO2. The measured TATs of most hemoglobin and potassium determinations did not meet clinician goals. In contrast to laboratorians, the majority of clinicians defined a TAT start time as test ordering, and a TAT ending time as result reporting. We recommend laboratorians and clinicians mutually agree on the definition of TAT, jointly develop timeliness goals, and together improve TAT performance to fulfill these goals.

Diagnostic Tests, Routine↗
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↗
PubMed1992

Evaluation of capillary collection system for HbA1c specimens.

OBJECTIVE: We evaluated the accuracy and stability of a capillary HbA1c collection system for use with a high-performance liquid chromatography analyzer. RESEARCH DESIGN AND METHODS: The collection system requires that 5 ul blood is drawn into a calibrated capillary tube, which is then placed into a vial of stabilizing solution and sent for analysis. The study was conducted on simultaneously drawn capillary and venous blood specimens from 47 pediatric diabetes patients. Accuracy was determined by comparing the capillary to the venous HbA1c values. Stability was measured by analyzing 17 capillary specimens over 3 wk. RESULTS: There was excellent agreement between the capillary and venous HbA1c values (capillary 0.959, venous +0.494, R2 = 98.7%). The capillary HbA1c values were 0.2% higher than the venous HbA1c values and decreased gradually over time (0.1% HbA1c/week) when stored at room temperature. CONCLUSIONS: The Bio-Rad (Richmond, CA) collection system is accurate, stable, and simple to use.

Blood Specimen Collection↗
PubMed1992

Achieving the Health Care Financing Administration limits by quality improvement and quality control. A real-world example.

With the enactment of the Clinical Laboratory Improvement Amendments of 1988 (CLIA 88), the federal government is now using proficiency testing as the primary indicator of laboratory quality. Laboratories with proficiency test failures are now at risk of a variety of harsh penalties including large monetary fines and suspension of operations. To minimize the risk of failed proficiency testing, we initiated a continuous quality improvement program in our general chemistry laboratory in conjunction with the use of a new survey-validated quality control product. This article describes the quality improvement program and our success in reducing the long-term random error in general chemistry. Despite our improvement program, significant analytical errors (greater than 30% of the CLIA limits) still exist in analytes measured by our chemistry analyzer. These errors are present in nearly the same analytes measured by other common chemistry analyzers indicating the need for improvement in their design and manufacture.

Blood Chemical Analysis↗
PubMed1992

Emergency department stat test turnaround times. A College of American Pathologists' Q-Probes study for potassium and hemoglobin.

We report aggregate turnaround times (TATs) from phlebotomy to result reporting of emergency department patients' hemoglobin and potassium results for 722 subscribers to the College of American Pathologists Q-Probes program. Approximately 40,000 specimens were obtained for each analyte. Median interinstitutional TAT time of 25 minutes for hemoglobin and 36 minutes for potassium varied little by shift, weekdays, or weekends. The type of personnel collecting the specimen and the method of specimen transport were the most important factors affecting TATs. Specimen transit times accounted for approximately one third of the total TATs, but when couriers transported hemoglobin specimens, the median transit time was equivalent to the median intralaboratory test TAT. The influence of various measures used to improve test transit and TATs is presented.

Bloodletting↗
PubMed1991

Laboratory phlebotomy. College of American Pathologists Q-Probe study of patient satisfaction and complications in 23,783 patients.

Outpatients from 630 institutions participated in a phlebotomy module of Q-Probes, a quality assurance program of the College of American Pathologists, Northfield, Ill. This module assessed patient outcome measurements of complications, discomfort, and satisfaction with the phlebotomy procedure. Of the 29,700 ostensibly healthy individuals registered, 80.1% returned postcards containing measurements and assessments they made about the procedure and information recorded by the phlebotomist. The median time required for phlebotomy was 6 minutes, with 25% of patients requiring less than 5 minutes and 10% more than 21 minutes for completion of the procedure. The average number of phlebotomy attempts per patient was 1.03, with 95 patients (0.4%) experiencing three to 11 attempts. Ecchymoses occurred in 4048 (16.6%) attempts, with the median size of ecchymosis being 15.1 mm. On the average, an outstanding employee was identified by patients 46.6% of the time. The discomfort caused by the needle puncture was more than expected by 35.3% of patients. Although 98.6% of the patients were satisfied, 336 patients were dissatisfied with the procedure. We conclude that the technical skills of phlebotomists and patient satisfaction with phlebotomy are outstanding, but that patient discomfort from the procedure needs to be minimized.

Bloodletting↗
PubMed1990

Relationship of quality goals and measurement performance to the selection of quality control procedures for multi-channel haematology analysers.

An approach is described for selecting QC procedures based on goals for analytical quality, the performance characteristics of the measurement procedure (imprecision, bias, frequency of errors), and the performance characteristics of the control procedure (probabilities for error detection and false rejection). Performance characteristics of stable sample QC procedures and patient data QC procedures (retained patient specimens, Bull's single-rule algorithm, Bull's multi-rule algorithm) are compared to determine when to apply these different QC procedures to multichannel hematology analysers. Precise, stable methods may be controlled using Bull's single-rule algorithm; less precise, less stable methods require Bull's multi-rule algorithm, retained patient specimens, or stable sample QC procedures; imprecise and unstable methods are best controlled using stable sample QC procedures. "Multi-stage" designs may employ stable samples for "startup" testing, retained patient specimens for short term monitoring, and Bull's single-rule algorithm for long term monitoring.

Algorithms↗
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↗
PubMed1988

Longitudinal study of error prevalence in Pennsylvania physicians' office laboratories.

We examined the results of the low-volume-laboratory proficiency testing program for new physician office participants in the Commonwealth of Pennsylvania. Serum glucose, hemoglobin, urinalysis, throat culture, urine culture, and Gram's stain were included in the study. Quarterly error rates for each analyte were determined; between one fourth and all of the laboratories that made at least one error during the first two quarters of proficiency testing made at least one more error in the same analyte during the subsequent two quarters. We show that participation in the quarterly proficiency testing program for a 12- to 15-month period did not lead to a measurable increase in performance. For proficiency testing to be effective, we suggest that it be supplemented by additional methods to lower error rates, such as regulation or intensive consultation and training services for personnel of physicians' office laboratories.

Diagnostic Tests, Routine↗
PubMed1988

An optimized quality control procedure for hematology analyzers with the use of retained patient specimens.

The authors propose guidelines for the use of retained patient specimens for the quality control of multichannel hematology analyzers. They demonstrate that control limits for patient specimen replicates may be derived from the long-term standard deviations (s) of commercial whole blood controls. They then use computer stimulation of the Coulter multichannel hematology instrument to determine power functions of various procedures using retained specimens. These power functions show that the use of three patient specimens and +/- 2 s limits are optimal for the detection of systematic error. They recommend that three different, previously analyzed normal range specimens be periodically analyzed, e.g., at eight-hour intervals. The differences between the current and original measurements should then be calculated and compared with their +/- 2 s limits. If at least two of the three differences for any directly measured parameter exceed the +/- 2 s limits, there will be a high probability of significant analytic error. Because the power functions of the derived red blood cell parameters, hematocrit, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration demonstrate relatively low error detection capabilities, the authors recommend that these parameters not be monitored with the retained patient specimen procedure.

Hematology↗
PubMed1988

Survey of special practices associated with College of American Pathologists proficiency testing in the Commonwealth of Pennsylvania.

A questionnaire concerned with special practices associated with proficiency testing was sent to the Chemistry Supervisor, Hematology Supervisor, and Chief Pathologist of 190 Pennsylvania hospital laboratories. Responses were received from 156 hospitals (82.1%) and included responses from 131 chemistry supervisors, 108 hematology supervisors, and 92 chief pathologists. The vast majority of respondents (85% to 95%) indicated moderate to great pressure to score acceptably. The survey showed a high prevalence of special practices, including analysis of controls just prior to survey specimens (23% to 42%), analysis in duplicate on a single instrument (52% to 88%), analysis on more than one instrument (17% to 31%), analysis on two or more separate days (20% to 39%), and delay of testing until an instrument is "working better" (24% to 34%). Approximately 63% of chemistry results and 72% of hematology results are reported as averages or medians. Pathologists consistently reported a lower prevalence of special practices than did laboratory supervisors. These high prevalences of special practices associated with proficiency testing specimens have important implications for proficiency testing programs.

Academies and Institutes↗
PubMed1987

Evaluation of the average of patients: application to endocrine assays.

Recent work (Cembrowski et al, Am J Clin Pathol 1984;81:492-499) has shown that the average of selected patient data can theoretically be used to demonstrate systematic errors. We formerly demonstrate that the sensitivity or power of the 'average of patients' (AOP) is related to the index (NpSw2)/Sp2 where Np is the number of patient results averaged, Sw the within-run component of the standard deviation of the analytical method and Sp the standard deviation of the trimmed population. The utility of the AOP can therefore be assessed rapidly without power function curves or the calculation of the daily AOP itself. The index showed that, for 12 radioimmunoassays done in our laboratory, the power of the AOP was greatest for T3 uptake, then FTI, then T4. Daily AOP were followed for these tests with control results on parallel Shewhart plots. We also applied an exponential smoothing procedure on the AOP and control results to improve trend detection. These analyses demonstrated that the AOP can improve the detection of systematic errors and the differentiation of true errors from errors affecting only control specimens.

Endocrine System Diseases↗
PubMed1987

Performance characteristics of Bull's multirule algorithm for the quality control of multichannel hematology analyzers.

The multirule quality control procedure for interpreting Bull's moving averages, proposed by Levy and colleagues (Am J Clin Pathol 1986; 85: 719-721.), has been evaluated by computer simulation with the use of the approach of Cembrowski and Westgard (Am J Clin Pathol 1985; 83: 337-345.). With this procedure, a batch of patient specimens is rejected if either of two criteria are satisfied: (1) the Bull's mean of one of the red blood cell indices is outside its 3% limits, or (2) the average of three consecutive Bull's means is outside its 2% limits. Power function curves were used to summarize the performance of the multirule approach and demonstrated error-detection capabilities that are superior to the more common implementation of Bull's algorithm using 3% limits for single Bull's means. The increased error detection achieved by the multirule procedure allows shifts in hemoglobin and mean corpuscular volume to be more readily detected but also results in the detection of small shifts in red blood cell count. A modified multirule procedure was also tested and was found to be ineffective. The authors recommend the multirule of Levy and colleagues but caution that its use may result in the detection of small shifts in the red blood cell count.

Algorithms↗
PubMed1987

Prototype quantitative assay for fibrinogen/fibrin degradation products. Clinical evaluation.

A new quantitative assay for fibrinogen/fibrin degradation products (FDPs) was clinically evaluated in 123 tertiary-care patients for whom the standard semiquantitative FDP assay had previously been ordered. On the basis of a comprehensive chart review, 24 patients were categorized as having disseminated intravascular coagulation (DIC), 84 were considered not to have had DIC, ten had fibrinolysis (nine of ten streptokinase induced), and five had a complicated coagulopathy whose exact nature could not be determined. The quantitative and semiquantitative FDP values were significantly correlated. However, the FDP level indicative of DIC was lower by the quantitative assay than by the semiquantitative assay, approximately 18 mg/L vs 40 mg/L, respectively. The advantages of the quantitative over the semiquantitative assay included improved precision and ability to closely monitor changes in the severity of the coagulopathy.

Disseminated Intravascular Coagulation↗
PubMed1987

Detecting errors in blood-gas measurement by analysis with two instruments.

We performed a two-stage prospective evaluation of the error detection capabilities of duplicate analysis of blood-gas specimens. In the first stage we analyzed 1601 specimens with a Corning Model 175 blood-gas analyzer as the test instrument and a Corning Model 178 analyzer as the reference instrument, and in the second stage we analyzed 1544 specimens with two Model 178 analyzers. In each stage the designated reference instrument underwent troubleshooting whenever an analytical error was detected; the test instrument underwent troubleshooting only when error conditions were indicated by means other than duplicate analysis. An error was considered to have occurred if the difference between the duplicate analyses exceeded 0.02 (for pH), 0.53 kPa, i.e., 4 mmHg (pCO2), or 7% (pO2). The number of specimens for which errors were detected was 97 (6.1%) in the first stage, 23 (1.5%) in the second. For each analyte more errors were detected with the Model 175 analyzer (of older design) than with the newer Model 178 analyzer. Furthermore, in certain periods associated with the use of particular electrodes there were very high error rates for individual analytes: 8% for pCO2, 18% for pO2. We conclude that duplicate analysis should be considered as a possible required standard for error detection.

Blood Gas Analysis↗
PubMed1986

Diagnostic efficacy of six plasma proteins in evaluating consumptive coagulopathies. Use of receiver operating characteristic curves to compare antithrombin III, plasminogen, alpha 2-plasmin inhibitor, fibronectin, prothrombin, and protein C.

Six coagulation proteins were measured in 79 consecutive patients referred to the coagulation service for suspected disseminated intravascular coagulation. Antithrombin III, plasminogen, and alpha 2-plasmin inhibitor were measured with fluorescent substrate assays. Fibronectin, prothrombin, and protein C were measured with electroimmunoassays. Using history and physical findings and the results of a coagulation screen (prothrombin time, partial thromboplastin time, fibrinogen, fibrin[ogen] degradation products, platelet count, and peripheral smear), the 79 patients were classified into five categories: no disseminated intravascular coagulation (n = 21), elevated fibrin(ogen) degradation products without other evidence of coagulopathy (n = 44), defibrination syndrome (n = 9), microangiopathic thrombocytopenic purpura (n = 4), and primary fibrinolysis (n = 1). Because the sensitivity and specificity of each of the proteins could not easily be compared, receiver operating characteristic (ROC) curves and areas under the ROC curves were calculated for each of the six proteins as well as for the tests of the coagulation screen. The ROC curves indicated that, apart from plasminogen, the other coagulation proteins provided little additional information about the classification of the coagulopathy.

Antithrombin III↗
PubMed1986

Capillary blood glucose screening for gestational diabetes: a preliminary investigation.

Home glucose monitoring with the use of reflectance meters is an important adjunct in the care of pregnant women with insulin-dependent diabetes. The accuracy of reflectance meters for the assay of capillary glucose specimens has been well documented. The present preliminary study was undertaken to determine the utility of outpatient screening for gestational diabetes mellitus with the use of a reflectance meter (Accu-Chek, Boehringer Mannheim Co.). One hundred twenty-five patients in our high-risk practice had a standard 50 gm glucose load at 26 to 28 weeks' gestation. Capillary glucose values were measured on site with the Accu-Chek. Venous plasma glucose levels were measured by the central laboratory chemistry analyzer. While the laboratory (x) and meter (y) glucose determinations between the two sets of values were highly correlated (R = 0.89, p less than 0.001), there was a significant difference in their average values (x = 111.74, y = 136.35, p less than 0.0001). With the use of a receiver operator characteristic curve, a meter value of 160 mg/dl was determined as the optimal threshold for performing a 3-hour glucose tolerance test. The sensitivity and specificity with the use of a meter value of 160 mg/dl were 93% and 96%, respectively, for detecting an abnormal screening test in venous plasma (greater than or equal to 135 mg/dl). A total of 32 glucose tolerance tests were performed, with four patients included who had venous values less than 135 mg/dl. All eight patients with gestational diabetes mellitus were correctly identified. These data suggest that a glucose reflectance meter can be used for accurate outpatient screening of gestational diabetes mellitus. The potential advantages of capillary blood glucose screening include both cost and efficiency. Patients with abnormal screening values can be promptly identified and scheduled for a follow-up 3-hour glucose tolerance test.

Blood Glucose↗