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. All the steps from test ordering to results reporting should be monitored and steps taken to improve the processes. Various strategies to improve TAT at each step in the testing process are discussed.

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 10.0 ng/mL), to analyze these reference materials in a large number of clinical laboratories using a variety of commercially available methods, and to characterize the molecular forms of PSA in them. METHODS: Units of serum from healthy individuals and from patients with varying degrees of elevated PSA were pooled, lyophilized, and distributed along with conventionally prepared, semen-supplemented proficiency testing samples to laboratories participating in the College of American Pathologists Basic Ligand Survey. The reference material and one of the standard Survey samples were fractionated by Sephacryl S-200-HR gel filtration chromatography. RESULTS: The Abbott IMx, Hybritech Tandem-E, Hybritech Tandem-R, and Tosoh AIA-Pack all measured PSA in the reference material fairly equally (agreement within +/- 12%). In contrast, the Abbott IMx results in the semen-supplemented Survey specimens were as much as 1.8-fold higher than the other three assays. Characterization of the molecular forms showed the reference material was approximately 90% alpha 1-antichymotrypsin-bound PSA, whereas the semen-supplemented Survey specimens were approximately 40% alpha 1-antichymotrypsin-bound PSA, which largely explained the difference in assay recoveries. CONCLUSIONS: Semen-free materials containing only endogenous PSA much more closely mimic real clinical specimens and should prove useful in efforts to standardize clinical PSA assays.

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. Variation in hormonal forms appears to contribute significantly to the wide variation in immunoassay results for these polypeptide hormones. Subunits and isoforms of the polypeptide hormones can overreact or underreact in monoclonal antibody assays. The underreaction or overreaction can occur with standards, controls, and patient specimens as well as with the assay label.

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. Fluorescence polarization immunoassay and time-resolved fluorescence using the lanthanides are two of the newer fluorescence techniques. Luminescent labels, such as acridinium esters, show promise because of their stability, sensitivity, and ease of detection. Several new particle label techniques have been introduced, perhaps two of the most interesting of which are sol particle and liposome labels. Advantages and disadvantages of the newer labels are compared with those of radioactivity.

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 (3.6% to 0.3%) during the study period. Episodes in which red blood cells (RBC) or fresh frozen plasma (FFP) alone and RBC and FFP together were transfused comprised almost all of the cases that were unjustified by peer review. The findings indicated that, although comprehensive review may document the overall appropriateness of clinical transfusion practice, more detailed profiling of clinical circumstances of each episode is necessary to provide convincing arguments for major revisions in hemotherapy practice.

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. When the BSA standards from the Lowry procedure were assayed with the other methods, results ranged from 74 to 141% of expected. For three other protein standards, reactivity among the six methods varied almost twofold. Comparison of Lowry protein concentrations in cytosols from 46 tumors biopsies with other methods indicated best agreement was with an automated turbidometric (TCA) or a Coomassie dyebinding procedure. Use of protein standardization for the two direct spectrophotometric procedures decreased overestimation of receptor protein concentrations. Because receptor concentration is the quotient of receptor quantity and protein concentrations, tissue receptor results are dependent in part on standardization and choice of protein 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.

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.

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.

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. The use of nonhemolyzed plasma specimens and prompt centrifugation, separation of plasma, and ammonia determination apparently were important in avoiding such increases, the duration of contact between plasma and cells being the most important factor. Lower temperatures had minimal effect on whole-blood storage and centrifugation, but retarded increases in ammonia in stored plasma. We conclude that procedures for collection and storage of specimens for ammonia determinations should be standardized and strictly observed.

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 0.2% non-immune rabbit serum to the labelled antibody. Two other radioimmunoassays gave results with these sera that were not falsely lowered. The interference was shown to be due to human IgG reactive with rabbit serum, the specificity of the interfering antibody being similar in all affected sera. Human antibodies directed against immunoassay reagents may lead to spuriously increased or decreased immunoassay results depending on the specific reagents involved.

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. In general, biases appeared to be proportional to analyte level. For some analytes, biases with liquid material were less than with lyophilized material, but for most analytes, biases were greater with liquid than lyophilized material. However, when liquid material is used for monitoring interlaboratory precision, the consequences of analytic biases are minimized because of large pool sizes.

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. Recent advances in the practice of quality control include use of new types of quality control materials, changing concepts of what is out of control, and the introduction of microcomputer applications.

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. The bacteria led to osmometer dysfunction presumably by acting as a nidus for crystallization and preventing proper supercooling of specimens.

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. When we added 2 mL of nonimmune rabbit serum per liter to the labeled IRMA rabbit antibody reagent and reassayed the five affected specimens, the results were within the reference interval. Smaller additions partly corrected the TSH values, but nonimmune sera of eight other species had no effect. Substitution of goat solid-phase antibody decreased, but did not eliminate, the increases in TSH in three of the five affected sera. Chromatographic properties, results of rheumatoid factor testing, and measurement of human anti-rabbit immunoglobulin suggest that the interference is ascribable to an antibody of the IgG class that reacts with rabbit antibody. Evidently, antibody interference with IRMA procedures may be common in certain populations. It can be avoided by including nonimmune serum corresponding to the species used to produce reagent antibody.