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.

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.

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. Patients' electronic medical records were reviewed for clinical responses and patient outcomes. Of the 111,545 sodium results occurring during the study, 615 (0.6%) were critical. By using criteria of 120 mEq/L (120 mmol/L) or less and 155 mEq/L (155 mmol/L) or more, we found 166 critically low results and 447 critically high results. In hypernatremic and hyponatremic patients, the lengths of stay were increased above our average, and clinicians responded to more than 50% of results within 4 hours. The mortality rates of hyponatremic and hypernatremic inpatients were 19% and 48%, respectively. Disease severity as measured by length of stay and mortality indicated these critical limits should not be broadened.