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.

Context.-A common laboratory practice is to repeat critical values before reporting the test results to the clinical care provider. This may be an unnecessary step that delays the reporting of critical test results without adding value to the accuracy of the test result.Objectives.-To determine the proportions of repeated chemistry and hematology critical values that differ significantly from the original value as defined by the participating laboratory, to determine the threshold differences defined by the laboratory as clinically significant, and to determine the additional time required to analyze the repeat test.Design.-Participants prospectively reviewed critical test results for 4 laboratory tests: glucose, potassium, white blood cell count, and platelet count. Participants reported the following information: initial and repeated test result; time initial and repeat results were first known to laboratory staff; critical result notification time; if the repeat result was still a critical result; if the repeat result was significantly different from the initial result, as judged by the laboratory professional or policy; significant difference threshold, as defined by the laboratory; the make and model of the instrument used for primary and repeat testing.Results.-Routine, repeat analysis of critical values is a common practice. Most laboratories did not formally define a significant difference between repeat results. Repeated results were rarely considered significantly different. Median repeated times were at least 17 to 21 minutes for 10% of laboratories. Twenty percent of laboratories reported at least 1 incident in the last calendar year of delayed result reporting that clinicians indicated had adversely affected patient care.Conclusion.-Routine repeat analysis of automated chemistry and hematology critical values is unlikely to be clinically useful and may adversely affect patient care.( This Q-Probes study was designed to determine the proportion of repeated critical results, the proportion of

The mean prolactin concentration during sleep and the per cent change (increase) and increment in the nocturnal elevation of plasma prolactin concentrations were significantly reduced (P less than .01, less than .01, and less than .001, respectively) in 6 untreated patients with clinically active Cushing's disease, compared with concentrations seen in normal subjects. There was no significant difference between mean-awake and mean-sleep plasma prolactin concentration in these patients, in contrast to that seen in normal subjects. In contrast, patients with hypercorticism secondary to adrenal adenoma (n = 2) or receiving long-term, high-dose corticosteroid therapy (n = 6) did not differ significantly from normal subjects in the percentage change seen in the nocturnal elevation of their plasma prolactin concentrations. Although mean prolactin concentration during sleep was reduced in these two categories of hypercorticism, a significant difference was still present between mean-awake and mean-sleep plasma prolactin concentration. (The nocturnal increment in plasma prolactin concentrations in these patients with hypercorticism compared with that of normal subjects was reduced, P less than .02). The difference between the percentage change and nocturnal increment observed in patients with Cushing's disease versus that seen in these two categories of hypercorticism was significant at P less than .02 and P less than .01, respectively. Four untreated patients with localized hypothalamic tumors also showed a significant reduction in the percentage change and increment in the nocturnal elevation of plasma prolactin concentrations (P less than .05 and P less than .02). In contrast to these findings, the prolactin responses to thyrotropin-releasing hormone (indicative of pituitary responsiveness) in patients with Cushing's disease, patients with adrenal adenoma, or those receiving chronic corticosteroid therapy, were all within the normal range seen in sex-matched control subjects. These findings provide additional evidence for the suggestion that there is altered hypothalamic function in patients with Cushing's disease.

Objective.—The rapid intraoperative parathyroid hormone assay is transforming the parathyroidectomy procedure. We present a review of the literature on the use of the assay as an adjunct to surgery. To our knowledge, this is the first review of the literature to encompass and compare all known primary studies of this assay in parathyroidectomy patients. Data Sources.—Articles were collected by searching MEDLINE databases using relevant terminology. The references of these articles were reviewed for additional studies. Supplementary articles pertinent to the parathyroidectomy procedure, preoperative parathyroid localization studies, and intraoperative parathyroid hormone assay development also were examined. Study Selection and Data Extraction.—One hundred sixty-five references were analyzed and categorized separately into groups. Data Synthesis.—The primary studies of intraoperative data on patients undergoing parathyroidectomy were compared when possible. Studies were analyzed by type of assay used, where performed, turnaround time, and efficiency of use. Reviews of the types of parathyroid surgery and preoperative localization were included for educational purposes. Conclusions.—The intraoperative parathyroid hormone assay is a useful adjunct to preoperative imaging and parathyroid surgery because of its unique ability to detect an occult residuum of hyperfunctioning parathyroid tissue. Use of this assay will obviate the need for frozen section in most routine cases. The test facilitates minimally invasive parathyroidectomy for single parathyroid adenomas, which, in turn, improves cost-effectiveness and cosmetic outcome. Its use in patients with known preoperative multiglandular disease is promising but requires further study.

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.

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We report our observations on day-to-day variation in serum ferritin, serum iron, total iron-binding capacity, and percent saturation of binding proteins with iron in 13 ostensibly healthy subjects during five weeks. The average intrasubject coefficients of variation were 14.5, 28.5, 4.8, and 28.0%, respectively. Precision studies on control samples showed greater within-assay and between-assay analytical variation for serum ferritin than for serum iron or total iron-binding capacity. Evidently, serum ferritin varies less in a given individual from day to day than do serum iron and percent iron saturation. Thus, a single measurement of serum ferritin may be a more reliable index of iron stores than an isolated determination of either serum iron or percent iron saturation.