The Cardiovascular Health Study is an observational cohort study of risk factors for cardiovascular disease in 5201 participants, ages > or = 65 years. We report the methods and quality-assurance results for blood procurement, processing, shipping, storage, and sample analysis used during the first examination period (May 1989-June 1990). The most frequent difficulty in phlebotomy and processing was the requirement of more than one venipuncture (in 2.6% of the participants). The CVs for control materials ranged from 0.93% for glucose to 10.7% for insulin; most were < 4%. In addition to standard quality-assurance methods, we applied two other methods: technical error calculation for replicates, and weighted linear regression to assess time trend in results of control materials. After outliers were excluded, technical error values ranged from 1.7 for uric acid to 18.8 for insulin. Factor VII and factor VIII had slight trends over the 12-month analysis period. Results of quality-assurance analyses used to resolve problems were successful, thereby improving the second laboratory examination.

A monoclonal-antibody-based competitive radioimmunoassay for measuring human protein C is reported. With use of a purified protein C standard, the solid-phase assay was sensitive to less than 80 micrograms of protein C per liter. Intraassay CVs ranged from 5% to 8%; the inter-assay CV was 5.4%. Analytical recovery averaged 104% for purified protein C added to 10 samples of normal plasmas. The assay antibody could deplete plasma of all protein C, as determined by immunoaffinity chromatography followed by polyclonal Western blot analysis. Liquid-chromatographic gel permeation of plasma indicated a single immunoreactive species that had an appropriate molecular mass for monomeric protein C. Studies of monoclonal-antibody specificity showed no significant interferences by other vitamin K-dependent proteins. The mean protein C antigen concentration in plasma of 54 healthy subjects was 3.21 (SD 0.56) mg/L and was 1.51 (SD 0.52) mg/L for 22 patients on long-term warfarin therapy. Results of the monoclonal RIA correlated well with those by a polyclonal RIA also developed in our laboratory (r = 0.93) and an amidolytic functional assay (r = 0.88) for both normal plasma and plasma from patients on long-term warfarin therapy.

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Previous studies have shown that RBCs with residual WBCs stored in LISS and neomycin sulfate develop characteristics associated with enzyme-treated RBCs. During a mass screening program to antigen type donor RBCs, we observed that the Fy a antigens on a RBC sample from an in-house panel became non-detectable with anti-Fy a after incubation overnight in Diluent 2 from Micro Typing Systems, Inc. (MTS, Pompano Beach, FL). In response to this observation, we initiated an investigation to determine the cause. Tests were performed according to the manfacturer's instructions in MTS neutral gel cards or gel cards containing anti-IgG. We found that a reduction or loss of the Fy a , Fy b , and M antigens occurs when RBCs were prepared from samples containing residual WBCs (as a source of enzymes) and subsequently incubated in media containing neomycin sulfate and LISS. We showed that the effect did not occur in the absence of neomycin sulfate. RBC antigens can be altered in LISS if they have first been exposed to neomycin. We recommend restricting the use of RBCs suspended in MTS Diluent 2 to the day of dilution (as indicated in the package insert) if preparing reagent RBCs from sources that were not leukoreduced and were stored in the presence of neomycin.

Benchmarking data is a relatively new process in the home health care industry. But the results can assist an agency in the strategic planning— staffing needs and program development—for the present and future. This descriptive research project benchmarked home health care data at the national, state (ie, North Carolina), and local (ie, Triangle area: Raleigh, Durham, and Chapel Hill) level from varied sources. These data assisted the author in formulating recommendations and a projected 1- year schedule of visit volume that included full-time equivalent position needs and a productivity standard for a new home care agency.