Plain Vacutainer Research Articles

Seroprevalence of bvdv in cattle of different ages on 17 dairy farms in western England

Seroprevalence of <scp>bvdv</scp> in cattle of different ages on 17 dairy farms in western England

Effects of Repeated Freeze-Thaw Cycles on Concentrations of Cholesterol, Micronutrients, and Hormones in Human Plasma and Serum

The effects of repeated freeze-thaw cycles on concentrations of various analytes in plasma or serum were of little interest until the growth of plasma and serum banks during the latter part of the 20th century. By 1996, the number of such banks used primarily for cancer research had grown to 115 (1). Many also exist for other purposes, such as the WHO Serum Reference Banks (2) and banks associated with cardiovascular studies such as the Multiple Risk Factor Intervention Trial (MRFIT) and the Atherosclerosis Risk in Communities (ARIC) Study (3)(4). Although the need for repeated freezing and thawing of samples can be minimized by storing banked specimens in several small containers (5), it often is necessary to use plasma or serum that has already undergone one or more freeze-thaw cycles. When this occurs, reviewers of research protocols or manuscripts may question the validity of data obtained from these specimens. The scientific literature provides few answers to such questions. Medline contains no appropriate key word or phrase for searching; comments on the effects of freeze-thaw cycles often are limited to a few sentences in publications that focus on stability during long-term storage or on assay methodology. The present study was designed to add information to this sparse literature. In 1991, 10 healthy adult volunteers, 5 men and 5 women, each donated 120 mL of blood. The purpose of the study was explained to each person along with the risks and lack of individual benefit. Approval of the study was granted by the Committee on Human Volunteers of the Johns Hopkins School of Hygiene and Public Health before study initiation. Blood was collected into three 20-mL Vacutainer Tubes containing 286 USP units of sodium heparin (cat. no. 6406; Becton Dickinson) to obtain plasma, and into four 15-mL plain Vacutainer Tubes …

Effects of storage temperature and time before centrifugation on ionized calcium in blood collected in plain vacutainer tubes and silicone-separator (SST) tubes.

We studied the stability of ionized calcium and pH in samples stored at either room temperature or 4 degrees C, in centrifuged and uncentrifuged blood-collection tubes and in centrifuged tubes containing a silicone-separator gel (SST tubes). At room temperature, in uncentrifuged blood from healthy individuals, mean ionized calcium usually increased no more than 10 mumol/L per hour; at 4 degrees C it did not change detectably for 70 h. This stability was fortuitous, however: the concentrations of both hydrogen and lactate ions in these samples increased, apparently with offsetting effects on the concentration of ionized calcium. Blood stored for 70 h at 4 degrees C in centrifuged SST tubes, although showing a slightly greater change in ionized calcium, had less change of pH and no change in the ionized calcium corrected to pH 7.4. In 11 heparinized whole-blood samples from eight patients in intensive care, the mean change per hour in ionized calcium and pH after storage at room temperature was +10 mumol/L and -0.04 units, respectively.