Fibronectin In Commercial Coagulation Factor Concentrates And Response Of Fibronectin Plasma Levels To Infusions

Fibronectin (FN) was assayed via a commercial mono-specific antiserum (Cappell Labs Inc.) using a Laurel immuno- electrophoretic assay with a pool of 10 normal plasmas as control. This control pool was arbitrarily given the FN concentration of 100% containing 300 μg FN/ml plasma. FN was measured in various lots of different commercial factor concentrates and cryoprecipitate. The concentration of FN varied widely among 3 different commercially available FVIII concentrates. One product showed a mean level of 2,376% (6 lots), a second 415% (4 lots) and a third 903% (2 lots). The average FN level of 3 cryoprecipitate preparations was 576%. FN was not present in 3 lots of one commercial FIX concentrate. FN was assayed in the plasma of 12 patients with hemophilia before and immediately after factor concentrate/cryoprecipitate infusion for therapeutic purposes. The response of the plasma FN level to the infusion was assessed by determining the total FN infused (mg), the observed rise in plasma (%) and the absolute FN amount producing a 1% rise in plasma level. The quantity of FN infused (a function of volume of infusate and concentration of FN) varied widely from 1.19 mg to 17.0 mg total. The observed rise depended inter alia on absolute FN infused and body weight. This ranged between 0 and 139%. Cryoprecipitate produced the greatest rise of plasma FN level per unit weight of FN infused. The commercial concentrates showed a wide spectrum of plasma FN responses in most cases requiring greater absolute FN infusion doses than cryoprecipitate for each 1% of increase in plasma level. These results indicate that FN is a major contaminant of some commercial Factor VIII concentrates. It is possible that FN is denatured by the concentration process resulting in very rapid removal of infused FN from the circulation.

INTERNAL QUALITY CONTROL OF RADIOIMMUNOASSAYS: MONITORING OF ERROR

A cumulative sum technique has been specially designed to monitor the error between replicate determinations made on quality control plasma for consecutive batches of assays. This procedure has played a vital role in assessing assay performance. Special consideration has been given to small sample sizes (n = 2 or 3) which is generally the rule rather than the exception in many situations. This technique has been applied to numerous steroid radioimmunoassays and has ensured that both the mean value and the standard error of hormone levels of a quality control pool were under control. Data from routine assays of oestriol and testosterone in plasma from women are presented. Since this technique provides a sensitive measure of monitoring error, it assists the endocrinologist in elucidating statistical inferences which are a manifestation of assay performance.

High-density lipoproteins estimated by an enzymatic cholesterol procedure, with a centrifugal analyzer.

We describe an assay for high-density lipoprotein cholesterol, adapted to a centrifugal analyzer, the GEMSAEC System 3, which includes use of an increased Mn2+concentration (91 mmol/liter) [J. Lipid Res. 19, 65 (1978)] and ethylenediaminetetraacetate [Clin. Chem. 22, 98 (1976)]. Modifications to the GEMSAEC system include reducing the mixing burst and preconditioning the sample tip. Accuracy of this procedure, as assessed by analysis of a control pool from the Center for Disease Control, was 99.2%. Day-to-day precision for two control pools was 320 +/- 13 and 506 +/- 17 mg/liter. Serum sample volume was decreased to 0.5 ml. In blanks with heparin/Mn2+ present, the pseudocholesterol concentrations resulting from a reaction of the enzymatic cholesterol reagent and the heparin/Mn2+ precipitating reagent depend on the source of the enzymatic reagent and appear to be enhanced slightly by the use of ethylenediaminetetraacetate. Pseudocholesterol concentrations reach a maximum at heparin/Mn2+ concentrations well below those needed to completely precipitate the low-density and very-low-density lipoprotein fractions. Population reference values were obtained from analyses done on 224 local physicians (mean: male, 500 mg/liter; female, 620 mg/liter) and 156 ambulatory patients (mean: male, 463 mg/liter; female, 553 mg/liter).