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Biomedical subjects

P G Catrou

Publications and source records attributed to P G Catrou.

At least 19 recordsLinked to original sources
PubMed1998

Simplified interpretative format for assessing test interference: studies with hemoglobin-based oxygen carrier solutions.

Substances such as hemoglobin that interfere with analytical processes are recognized as a frequent source of error in laboratory medicine. Standard guidelines for assessment of test interferences assume that interference effects are not related to the concentration of the analyte being measured. However, previous investigations have demonstrated that interference effects can be markedly different, depending on the concentrations of interferent and analyte within the specimen. An experimental protocol for investigating these different types of interference effects has been developed. This protocol utilizes an orthogonally arranged matrix with progressively increasing concentrations of analyte and interferent. Evaluation of the measured analyte concentrations in specimens within the matrix using multiple regression analysis allows the magnitude, direction, and significance of each type of interference to be determined. Unfortunately, implementation of the interference data derived from the multiple regression analysis for judging the clinical acceptability of test results when an interferent is present is difficult. We describe a two-dimensional graphical format for evaluating the clinical acceptability of test results, based on criteria established under the Clinical Laboratory Improvement Amendments of 1988, in specimens containing hemoglobin-based oxygen carrier solutions.

Aspirin↗
PubMed1995

Enzymatic markers of gallstone-induced pancreatitis identified by ROC curve analysis, discriminant analysis, logistic regression, likelihood ratios, and information theory.

We investigated the diagnostic utility of frequent serial determinations of aspartate aminotransferase, alanine aminotransferase (ALT), lipase, amylase, and the lipase/amylase (L/A) ratio for distinguishing patients with acute pancreatitis due to biliary obstruction from those with acute pancreatitis due to other pathogenesis. Analyzed were enzyme activities obtained at admission and peak enzyme activities identified retrospectively from serial measurements in 53 patients with acute pancreatitis due to various causes. We evaluated the data with multiple statistical tools. Discriminant analysis and logistic regression revealed the diagnostic significance of ALT at initial and peak values, and the maximum information provided by peak ALT was confirmed by both logistic regression and stratum-specific likelihood ratios. Stratum-specific likelihood ratios showed peak ALT > 150 U/L was highly diagnostic of biliary pancreatitis. The L/A ratio, either at admission or at peak, was the only other significant variable for identifying patients with acute pancreatitis due to biliary obstruction. A multivariate logistic discriminant function including ALT and the L/A ratio significantly discriminated biliary acute pancreatitis from pancreatitis due to other causes. Evaluation of initial and peak enzyme data by information theory revealed that the optimal test depended on disease prevalence. Initial ALT activities were the test of choice for identifying biliary pancreatitis, up to a disease prevalence of approximately 0.75. At disease prevalence > 0.75, the initial L/A ratio provided the greatest amount of diagnostic information.

Acute Disease↗
PubMed1993

Diagnostic accuracy of pancreatic enzymes evaluated by use of multivariate data analysis.

We analyzed pancreatic enzyme data from 508 patients with suspected pancreatitis by neural network analysis, by an Expert multirule generation protocol, and by receiver-operator characteristic (ROC) curve analysis of a single test result. Neural network analysis showed that use of lipase provided the best means for diagnosing pancreatitis. Diagnostic accuracies achieved by using amylase only, lipase only, and amylase and lipase in combination were 76%, 82%, and 84%, respectively. Use of the Expert rule generation protocol provided a diagnostic accuracy of 92% when rules for single and multiple samplings were combined. ROC curve analysis for initial enzyme activities showed the maximal diagnostic accuracy to be 82% and 85% for amylase and lipase, respectively; use of peak enzyme activities yielded accuracies of 81% and 88%, respectively. The evaluation of laboratory test data should include analysis of the diagnostic accuracy of laboratory tests by multivariate techniques such as neural network analysis or an Expert systems approach. Multivariate analysis should allow for a more realistic assessment of the diagnosis accuracy of laboratory tests because all the available data are included in the evaluation.

Amylases↗
PubMed1993

Laboratory error undetectable by customary quality control/quality assurance monitors.

The preanalytical, analytical, and postanalytical rates of laboratory error have not been studied extensively. We evaluated the preanalytical, analytical, and postanalytical components of laboratory error in 438 consecutive samples submitted to a clinical chemistry laboratory for measurement of creatinine concentrations in plasma. We performed red blood cell antigen determinations to establish patient-sample identity, repeated analysis of creatinine in duplicate to detect analytical error, and tracking of patient specimens from receipt by the laboratory to entry of the laboratory result in the patient's information system record. We found a total error rate of 9.36%. A breakdown of the total error rate into its preanalytical, analytical, and postanalytical components revealed error rates of 0.00%, 8.90%, and 0.46%, respectively. These results suggest that preanalytical and postanalytical error, which are not usually detectable by common quality control strategies, are not major sources of laboratory error. Further work is needed to reduce the unacceptably high rate of analytical errors.

Chemistry, Clinical↗
PubMed1986

A comprehensive evaluation of the performance of duplicate prothrombin time and activated partial thromboplastin time assays.

An evaluation of the performance of duplicate prothrombin time (PT) and activated partial thromboplastin time (aPTT) assays was undertaken to develop analytical duplicate performance criteria in order to quantitate the risks associated with singlet versus duplicate procedures. Data were retrospectively collected from two hospital laboratories using two different coagulation systems. Included in the study were 6,391 patient samples; 3,047 PT, 3,334 aPTT, for a total of 12,782 data points. If a difference between duplicates of 5% or less is deemed analytically (or clinically) insignificant for PT, then fewer than 1% of the samples analyzed by either laboratory would require duplicates. If a difference between duplicates of 15% or less is deemed analytically (or clinically) insignificant for aPTT, then fewer than 2% of samples would exceed this limit for laboratory A, but 6.0% of samples from laboratory B exceeded this limit.

Blood Coagulation Tests↗
PubMed1985

Laboratory equipment maintenance contracts.

The increasing level of technical sophistication and complexity found in clinical laboratory instrumentation today more than ever demands careful attention to maintenance service needs. The time-worn caution for careful definition of requirements for acquisition of a system should also carry over to acquisition of maintenance service. Guidelines are presented for specifications of terms and conditions for maintenance service from the perspective of the laboratorian in the automated clinical laboratory.

Commerce↗
PubMed1985

Cobalamin malabsorption in three siblings due to an abnormal intrinsic factor that is markedly susceptible to acid and proteolysis.

Three siblings presented in their second year of life with megaloblastic anemia that responded to parenteral cobalamin (Cbl). Schilling tests were less than 1%, correcting to 5 to 15% after addition of hog intrinsic factor (IF). Gastric acid analysis and gastric biopsies were normal by light and electron microscopy. Gastric juice contained less than 3 pmol/ml of Cbl-binding ability due to IF (normal, 10-34 pmol/ml) and less than 2 pmol/ml of IF when measured with a radioimmunoassay (RIA) using normal human IF-[57Co]Cbl and rabbit anti-human IF serum (normal, 17-66 pmol/ml). However, RIA employing rabbit anti-hog IF serum gave values of 4-13 pmol/ml of IF (normal, 11-33 pmol/ml). This material had an apparent molecular weight of 40,000 (normal IF = 70,000). The IF from gastric biopsies appeared normal in terms of Cbl-binding ability, ileal binding, molecular weight, and both RIAs. This IF differed from normal mucosal IF, in that it lost its Cbl-binding ability when incubated at 37 degrees C at acid pH or in the presence of pepsin or trypsin. This loss was retarded when [57Co]Cbl was bound to the IF before these incubations. The stabilizing effects of neutralization and Cbl were also demonstrated in vivo. Schilling tests for the siblings of 0.4, 0.5, and 1.0% increased to 2.7, 5.7, and 4.3% (P less than 0.05), respectively, when the Schilling tests were repeated with the addition of NaHCO3 and cobinamide (which allows Cbl to bind immediately to IF). We conclude that Cbl malabsorption in these children is due to an abnormal IF that is markedly susceptible to acid and proteolytic enzymes which cause a decrease in its molecular weight and Cbl-binding ability and a loss of antigenic determinants that are recognized by the anti-human IF serum.

Anemia, Megaloblastic↗
PubMed1984

Estimating supply requirements for implementing a laboratory information system.

The implementation of a new laboratory information system requires the total commitment of all laboratory personnel. Difficulties both within and external to the lab are to be expected as the lab and the hospital staff learn to use the system. Proper planning prior to implementation will avert additional problems that can arise due to an inadequate supply inventory. The purpose of this paper is to discuss methods of estimating supply requirements, as well as to point out other operational considerations related to system start-up.

Computers↗
PubMed1981

Nine-cell diagnostic decision matrix. A model of the diagnostic process; a framework for evaluating diagnostic protocols.

A nine-cell diagnostic decision matrix is described. This matrix can be viewed dynamically as a model of the diagnostic process. The matrix provides for display of equivocal test results and test results of patients who have ill-defined or incompletely determined disease. The matrix represents an improved model for evaluating diagnostic test protocols. Diagnostic test characteristics related to this model are described. Potential advantages and uses of the model are discussed; among them are possibilities for development of improved diagnostic protocols and improved definitions of disease.

Decision Making↗
PubMed1981

Ranking diagnostic protocols--a proposed process based on use of the nine-cell diagnostic decision matrix.

A process for ranking competing diagnostic protocols for a specific disease is presented. The process incorporates the basic principles of medical decision making, and provides for the consideration of equivocal test results as well as results for patients who have ill-defined or incompletely defined disease. It provides a means for developing an a priori optimization process prior to ranking competing diagnostic algorithms. Methods for transferring ranking information among populations with widely differing disease prevalences are given.

Clinical Laboratory Techniques↗
PubMed1980

Clinical evaluation of an algorithm for interpreting biochemical profiles showing hyperbilirubinemia.

An interpretive algorithm for biochemical profiles showing an elevated serum bilirubin concentration has been evaluated, modified, and retested in a retrospective clinical study, and is now being used at Charity Hospital in New Orleans to aid in the generation of interpretive comments to accompany the laboratory report. Further attempts to assess the clinical usefulness of this policy seem merited.

Computers↗