Paraproteins are a common cause of interferences with automated chemistry methods.

Context: Previous studies have shown that paraproteins caused spurious results on individual analytes including total bilirubin (TBIL), direct bilirubin (DBIL), or HDL-cholesterol (HDL-C). Studies demonstrating paraprotein interferences with multiple analytes measured by different analyzers have not been reported.

Objective: To systemically investigate interferences of paraproteins on TBIL, DBIL, and HDL-C measured by the Roche MODULAR and the Olympus AU2700.

Blood transfusions leading to apparent hemoglobin C, S, and O-Arab hemoglobinopathies.

Context: Apparent hemoglobinopathies caused by blood transfusions rarely have been reported in the scientific literature.

Objective: To interpret the abnormal hemoglobins appearing as small peaks on hemoglobin chromatograms or electrophoresis membranes.

Design: In the clinical laboratories of a university hospital and a metropolitan hospital affiliated with a medical school, we interpreted hemoglobin chromatograms and electrophoresis membranes; correlated them with patients' medical, laboratory, and transfusion records; and when possible, identified the abnormal hemoglobin in the donors' transfusion segments.

Evaluation of serum and whole blood sodium critical values.

Laboratories are required to have a critical values policy as a patient safety measure. Serum sodium commonly is included in critical results lists, but a wide range of values are used. We studied all critical serum and whole blood sodium results called to clinicians during a 6-month period.

Spurious hemoglobin Barts caused by bilirubin: a common interference mimicking an uncommon hemoglobinopathy.

High-performance liquid chromatography (HPLC) is replacing electrophoresis for identification of hemoglobin variants. Our objective was to identify unknown tall peaks with elution times and shapes of hemoglobin Barts found on hemoglobin chromatograms that could not be confirmed by alkaline and acid gel electrophoresis. Of 90 specimens identified with this peak, 86 were from patients with hemoglobin SS.

Comparison of pooled fresh frozen serum to proficiency testing material in College of American Pathologists surveys: cortisol and immunoglobulin E.

Context: The College of American Pathologists (CAP) provides proficiency testing (PT) surveys to laboratories around the world.

Objectives: To compare diagnostic assay methods for serum/plasma cortisol and immunoglobulin (Ig) E in terms of their bias and precision, to determine how well CAP PT specimens simulate human serum, and to reassess proficiency test grading criteria in light of these findings.

Design: A participant-blinded, prospective trial.

Laboratory results. Timeliness as a quality attribute and strategy.

Although timeliness of results reporting has not been a major focus in clinical laboratories, there is increasing pressure from clinicians to report results rapidly. Even though there are only sparse data, timeliness in reporting of laboratory results undoubtedly affects clinician and patient satisfaction as well as length of hospital stay. Improving turnaround time (TAT) is a complex task involving education, equipment acquisition, and planning.

Production, analysis, and characterization of reference materials for prostate-specific antigen.

Objective: To produce a set of three reference materials that mimic sera from patients with prostate disorders in the prostate-specific antigen (PSA) concentration range important for clinical screening for prostate cancer (approximately 0.5, approximately 4.0, and approximately 10.

Review of the influence of polypeptide hormone forms on immunoassay results.

Various forms of the polypeptide hormones that occur in blood, fluids, or tissues can differ according to physiologic and pathologic states. Forms include subunits of luteinizing hormone, follicle-stimulating hormone, human chorionic gonadotropin, and thyroid-stimulating hormone. Hormonal isoforms occur for these hormones as well as for prolactin and growth hormone.

Immunoassay. Innovations in label technology.

The history and recent developments in label technology are reviewed. Because the new labels generally are used in both classic immunoassays and immunometric assays, a brief review of the advantages and disadvantages of each type of assay is included. Recent developments in enzyme labels, such as channeling techniques, enzyme acceptor-donor systems, and apoenzyme reactivation assays, are discussed.

Toward meaningful blood usage review: comprehensive monitoring of physician practice.

During a one-year period, all blood transfusions at an acute care Veterans Administration hospital were concurrently reviewed. Inappropriate transfusion episodes represented less than 2% of the total according to clinical criteria established for purposes of screening cases. The percentage of episodes reviewed that did not meet the screening criteria decreased progressively (3.

Protein method influences on calculation of tissue receptor concentration.

Many protein methods are used for estimation of tissue receptor concentration. The authors compared performance, analytic variability, and accuracy of six protein methods used in these calculations. They found the Lowry protein procedure standardized with bovine serum albumin (BSA), usually considered the reference method, to be the most imprecise and most time consuming method.

Controversies in thyroid function testing.

Thyroid function tests can be abnormal in certain patients in the absence of thyroid dysfunction. All thyroid function tests can be affected in these patients, including the free thyroxine assays and free thyroxine index. Familiarity with the conditions affecting thyroid function tests is necessary to avoid incorrect diagnosis and unnecessary testing.

Hypercortisolism.

The diagnostic evaluation of a patient with hypercortisolism should progress through screening and then confirmatory hormonal measurements. However, tests of the hypothalamic-pituitary-adrenal axis to predict the cause of hypercortisolism always should be viewed as providing supportive data, as exceptions that occur limit the usefulness of these tests. Familiarity with the diagnostic errors of the procedures is essential.

Pituitary tumors.

The most frequent pituitary neoplasm is the adenoma, which can produce signs and symptoms owing to mass effects or secretion of pituitary hormones. The authors discuss these mass effects of pituitary tumors on the endocrine system and excess hormone secretion by pituitary adenomas.

Influences of specimen processing and storage conditions on results for plasma ammonia.

Ammonia concentrations in plasma may increase because of contamination and deterioration of blood components during specimen handling and storage. Using replicate specimens from healthy volunteers, we studied influences of specimen processing and storage procedures on ammonia measurements made with a self-contained reagent system. Under some conditions, ammonia concentrations more than doubled.

Circulating human antibodies as a cause of falsely depressed ferritin values.

We have previously reported spuriously elevated values for serum thyrotropin (TSH) measured by immunoradiometric assay (IRMA). We tested those sera showing interference with the TSH assay in a ferritin IRMA which used 125I-rabbit antiferritin antibody and solid phase goat antiferritin antibody as reagents and spleen ferritin as standard. In this assay, we obtained falsely low ferritin values that were corrected by addition of 0.

Analytical biases with liquid quality control material.

Biases were compared for eight analytes determined using common chemistry instruments. Data for three levels of liquid control sera were obtained from over 350 laboratories participating in a quality control program. These data were contrasted with comparable results for lyophilized material and reported in a CAP proficiency survey.

Quality control for the clinical laboratory.

Quality control is a management discipline by which laboratories assure the validity of their results for bedside management of patients. The thrust of quality control has been the laboratory's efforts at improving analytic variability associated with the measurement process. Through increasing emphasis on automation and participation in laboratory improvement programs, laboratory imprecision and inaccuracy have decreased over the past 15 years.

Bacterial interference with urine osmolality measurements.

We report bacterial interference with urine osmolality measurements using an instrument based on the principle of freezing point depression. Although the exact nature of the interfering activity has not been defined, the phenomenon is associated with a bacterium, identified as Pseudomonas putida, and is removed from the specimens by filtration at 0.45 micron.

Incidence and mechanism of spurious increase in serum thyrotropin.

We previously reported spuriously high values for thyrotropin (TSH), presumably owing to an antibody in human serum that reacts with both reagent rabbit antibodies in an immunoradiometric assay (IRMA). We used this IRMA to measure TSH. Five of 20 sera from laboratory animal handlers showed spuriously high values.