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G S Cembrowski

Publications and source records attributed to G S Cembrowski.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1986

Use of patient data for quality control.

This article discusses how specific patient data algorithms can be used and optimized for laboratory quality control. These algorithms include delta checks, patient averages, and multivariate checks. With the increasing emphasis on cost containment, the intelligent use of these algorithms should become widespread.

Medical Records↗
PubMed1985

Quality control of multichannel hematology analyzers: evaluation of Bull's algorithm.

Bull's algorithm has been evaluated by computer simulation studies. Varying amounts of systematic analytic error were simulated in either hemoglobin (Hgb), red blood cell count (RBC), or mean corpuscular volume (MCV) with the resulting red blood cell indices averaged in batches of 20 using Bull's algorithm. The number of average indices outside the limits of 0.97 means and 1.03 means (means = stable patient mean index) was tabulated and plotted against the size of the systematic shift, expressed in multiples of the long-term analytic standard deviation (SD). The resulting plots, called power functions, show that Bull's algorithm can detect large shifts effectively and that its power increases with increasing batch number. Shifts less than 2 SD rarely are detected. The minimum error that is detected 50% of the time after nine consecutive batches is shown below: (Formula: see text) The simulation of populations with outlying indices, e.g., neonates and oncology patients, resulted in both decreased and increased power, depending on the proportion of outliers averaged, the index averaged, and the direction of the shift.

Adult↗
PubMed1985

A quantitative automated immunoassay for fibrinogen/fibrin degradation products.

We describe a prototype quantitative automated assay for fibrin and fibrinogen degradation products, a particle-enhanced turbidimetric inhibition immunoassay (PETINIA) in the Du Pont aca discrete clinical analyzer. This assay involves a latex particle reagent with covalently bound fibrinogen and a polyclonal antiserum raised in rabbits against human fibrinogen. A special secondary sample-collection tube quantitatively removes fibrinogen from citrated plasma and inhibits further fibrinolysis, independent of heparin concentration. The assay range is 0-100 mg/L, in fibrinogen equivalents. The CV for the assay is less than 10% when performed with the aca. Nonclottable fibrin and fibrinogen fragments are measured by the assay, the greatest sensitivity being directed at the E domain of the fibrinogen molecule. We illustrate with case studies the potential of this assay for providing clinical information not obtainable with currently available qualitative and semi-quantitative assays.

Adult↗
PubMed1984

Plasma fibronectin concentration in patients with acquired consumptive coagulopathies.

Plasma fibronectin was assayed in 179 hospitalized patients referred for workup of possible acquired coagulopathy. Based on laboratory results and chart review, these patients were classified as having no coagulopathy (N = 36), defibrination syndrome (N = 31), compensated defibrination syndrome (N = 100), microangiopathic thrombocytopenia (N = 7), and primary fibrinolysis (N = 5). Compared to patients with no coagulopathy, fibronectin concentration was reduced in patients with defibrination syndrome (p less than 0.005) and compensated defibrination syndrome (p less than 0.10). Fibronectin concentration was not reduced in patients with microangiopathic thrombocytopenia and primary fibrinolysis. In patients with defibrination syndrome, the reduction of fibronectin was correlated to the degree of liver impairment. This finding is consistent with the liver being the primary site of synthesis of plasma fibronectin. Fibronectin was significantly correlated to plasminogen and antithrombin III. The sensitivity of fibronectin for the diagnosis of coagulopathy is low except for patients with defibrination syndrome.

Antithrombin III↗
PubMed1984

Quality control of electrolyte analyzers. Evaluation of the anion gap average.

The authors have shown previously that averaging at least eight patient anion gaps provides a sensitive technic for the detection of systematic error in electrolyte analysis (Am J Clin Pathol 79:688-696, 1983). They conducted a retrospective and prospective evaluation of this technic on the ASTRA 4. One month of patient and control data were studied retrospectively and showed that 17/71 abnormally low patient anion gap averages were associated with violations in a multi-rule procedure, and 41/71 low averages were associated with violations in cusum, a more sensitive procedure. In the prospective study, a total of 36 runs of eight patient specimens with low anion gap averages (less than 7.5 mmol/L) were reanalyzed after appropriate recalibration and/or maintenance. Thirty-one of the 36 groups had significant changes in either Na (nine groups, delta Na = +1.5 mmol/L), Cl (14 groups; delta Cl = -1.8 mmol/L), or in both Na and Cl (eight groups; delta Na = +1.2 mmol/L; delta Cl = -0.9 mmol/L). Because the average error detected was small, the authors recommend that the average of anion gaps be used as an early indicator of drift. It must be used, however, in conjunction with standard quality control procedures such as the multi-rule approach.

Acid-Base Equilibrium↗
PubMed1984

Assessment of "Average of Normals" quality control procedures and guidelines for implementation.

The capabilities of "Average of Normals" control procedures have been assessed by determining power functions, graphs of the probability of error detection versus the size of analytic error. The power functions indicate that the most important determinants of statistical power are the ratio of the standard deviation of the patient population (Sp) to the analytic standard deviation (Sa), Sp/Sa; the number of data points averaged (N); the control limits (probability for false rejection); truncation limits for selecting the population; and the magnitude of the population lying outside the truncation limits. General guidelines for the implementation of "Average of Normals" are provided, along with a nomogram for the selection of N as a function of Sp/Sa and the probability of error detection. Optimal performance of these procedures may require simulation studies on a per analyte basis.

Computers↗
PubMed1983

The use of CIE for the detection of Clostridium difficile toxin in stool filtrates: laboratory and clinical correlation.

Two CIE procedures (CIE-1, CIE-2) for the detection of Clostridium difficile in diarrheal stools were evaluated by comparison to cytotoxin assay and culture results and by comparison to a clinical likelihood of C. difficile-induced diarrhea. Using a combination of toxin assay and culture results for reference, the CIE-1 and CIE-2 procedures had sensitivities of 33% and 47%, specificities of 89% and 91%, and positive predictive values of 42% and 54%, respectively. Using clinical likelihood for reference, the best results were obtained by the CIE-2 method, which yielded a positive predictive value of 77%. Neither CIE procedure provided an acceptable sensitivity for the detection of C. difficile in stools.

Adult↗
PubMed1983

Use of anion gap for the quality control of electrolyte analyzers.

A simple model for the simulation of patient Na, CO2, Cl, and anion gap was formulated from patient electrolyte data. Analytical error, either random or systematic, was incorporated into the simulation of the electrolyte data and allowed study of the response of anion gap to error. Power functions, plots of probability of error detection vs. size of analytical error, were constructed and indicated a low probability of error detection when single patient specimens with abnormal anion gaps were reanalyzed. These power functions showed that pooling of the anion gap data by averaging consecutive anion gaps resulted in a high probability for detecting systematic error. We recommend, as a useful quality control procedure, averaging at least eight consecutive anion gaps and testing for a significant difference between the average and the established mean gap.

Acid-Base Equilibrium↗
PubMed1983

Evaluation of the accuracy of the diff3/50 with a cell by cell comparison.

The traditional approach to the evaluation of accuracy of discrete differential counters uses a graphic comparison of automated and manual counts. This type of comparison introduces so much sampling variation that significant differences often are obscured. To exclude this sampling variability, one of three technologists, a reference technologist and the Coulter diff3/50, each performed a differential count on exactly the same 100 cells of 47 normal and 56 abnormal blood smears. Linear regression analysis demonstrated excellent agreement between the technologists for all cell types with the exception of band neutrophils. Comparison of the instrument results with the technologists' results showed very good agreement for segmented neutrophils, lymphocytes, monocytes, and eosinophils. The identification of band neutrophils, basophils, immature granulocytes and atypical lymphocytes requires improvement. The overall performance is acceptable, with only 11 leukocytes, on the average normal smear, misclassified out of 100 normal leukocytes (four bands called segs, four segs called bands, and three non-neutrophils incorrectly classified). We recommend similar evaluations for all discrete differential counters.

Basophils↗
PubMed1982

Fluorometric assay of erythrocyte protoporphyrin: simple screening test for lead poisoning and iron deficiency.

Erythrocyte protoporphyrin levels are high in lead poisoning, iron deficiency and erythropoietic porphyria. On-site fluorometric assay was used to screen for raised blood levels in three groups of children in one city: 166 who were severely mentally retarded and lived in an institution, 88 who were moderately to severely mentally retarded and attending special schools but lived at home, and 128 who were of normal intelligence and attended a regular school. High erythrocyte protoporphyrin levels (40 micrograms/dl [0.7 mumol/l] or greater) were found in 14 of the children, each of whom was tested for further evidence of lead poisoning and iron deficiency. The two children found to have high blood lead levels (above 30 micrograms/dl [1.5 mumol/l]) were both living in the institution, were ambulatory and had pica. Of the other 12 children 8 had evidence of iron deficiency, though in 4 the probability of a true deficiency was low. The fluorometric assay of erythrocyte protoporphyrin may prove to be a simple method of screening for lead poisoning and iron deficiency.

Adolescent↗
PubMed1981

Probable fatal cardiac dysrhythmia secondary to diuretic-induced hypokalemia.

This case study describes the investigation of the sudden, unexpected death of a young, slightly hypertensive woman. She had a previous history pf serious hypokalemic-induced cardiac dysrhythmias associated with diuretic usage. Postmortem examination revealed no anatomic cause for her death. Her agonal plasma potassium, 5.4 mmol/L, seemed too low in light of her extreme acidosis, hypoxemia, and emergency treatment. Diuretic analysis indicated surreptitious ingestion of hydrochlorothiazide. Hypokalemia and the control of serum potassium concentration are discussed as are various modifiers of serum potassium.

Adult↗
PubMed1979

Statistical analysis of method comparison data. Testing normality.

A Lilliefors test of normality has been applied to data from precision and accuracy studies. Most data sets tested as non-normal. Simulation studies showed that the test is extremely sensitive to the rounded, narrowly distributed data that are typical of method performance studies in clinical chemistry. The Lilliefors test can be modified to be applicable to rounded data so that it gives fewer indications of non-normality. The authors conclude that the selection of a test of normality requires careful study of the properties of the test. Otherwise, the subsequent choice between parametric and nonparametric statistics may not be meaningful.

Chemistry, Clinical↗