Serum assay

The 25-OH-D Is further metabolized In the kidney to 1,25 dlhydroxycholecalclferol (1,25(OH)2D) which Is considered to be the major physiologically Important, tissue-active metabolite of vitamin D. It circulates In extremely low concentrations (< 100 pg/ml of serum). Assay of 1,25(OH)2D Is extremely tedious. It Is done by competitive binding technique using a combined Intestinal cell cytosol and chromatin binding system, biosynthetic 3h-1,25(OH)2D3 as labeled ligand and synthetic 1,25(0H)2D3 as standard (31). 

FIG. 18 Correlation between actual and found values of Na+ concentrations on serum assay with ISFETs based on sol-gel-derived membranes of bis(12-crown-4) (11). (From Ref. 49.)... 

Figure 11. Serum assays of diabetic rats after 14 days of treatment with 18 IU of bovine insulin, b.i.d., in polyacrylic and poly acrylic acid resins.

Serum ALP and total bilirubin (unconjugated and conjugated fractions) are traditionally used to monitor cholestatic injury. The ALP families of enzymes are zinc metalloproteases that are present in nearly all tissues. In the liver, ALP is immu-nolocalized to the microvili of the bile canaliculus [124]. Increased synthesis of ALP and its release into the circulation occurs within hours of cholestatic injury [129]. Serum assays of 5 -nucleotidase (5 -NT) or y-glutamyltransferase activity (GGT) are used to confirm the liver as the specific origin for the elevation of ALP. Increases in serum bilirubin or bile acids are usually the result of bile retention subsequent to impaired bile flow, increased production associated with accelerated erythrocyte destruction, or altered bilirubin metabolism [129]. 

Though better tolerated, significantly less bronchodilating activity vs theophylline. Serious dosing errors possible if dyphylline monitored with theophylline serum assays... 

The uses of constant-current coulometry for the determination of drugs in biological fluids are few, basically due to sensitivity restriction. Monforte and Purdy [46] have reported an assay for two allylic barbituric acid derivatives, sodium seconal and sodium sandoptal, with electrogenerated bromine as the titrant and biamperometry for endpoint detection. Quantitative bromination required an excess of bromine hence back titration with standard arsenite was performed. The assay required the formation of a protein-free filtrate of serum with tungstic acid, extraction into chloroform, and sample cleanup by back extraction, followed by coulometric titration with electrogenerated bromine. The protein precipitation step resulted in losses of compound due to coprecipitation. The recoveries of sodium seconal and sodium sandoptal carried through the serum assay were approximately 81 and 88%, respectively. Samples in the concentration range 7.5-50 pg/mL serum were analyzed by this procedure. 

All values for all serum assays in this section fall within the normal ranges for rats, reported in the literature (25,27). 

P8. Pezzilli, R., Morselli-Labate, A. M., Miniero, R., Barakat, B., Fiocchi, M., and Cappelletti, O., Simultaneous serum assayed lipase and interleukin-6 for early diagnosis and prognosis of acute pancreatitis. Clin. Chem. 45, 1762-1767 (1999). 

Examination of the bone marrow, although important, will only confirm that the hemopoiesis is megaloblastic. A deficiency of folic acid will also cause a megaloblastic anemia and it is not possible to identify the cause on the basis of morphology. A serum assay of both vitamins will usually indicate which is responsible. If the patient is vitamin B12 deficient, the next step is to carry out a vitamin B12 absorption test to confirm that the deficiency is due to a lack of intrinsic factor. Preferably this should not be done until the patient s vitamin B12 and hemoglobin levels have returned to normal, since the gastric and intestinal cells are also affected by a lack of vitamin B12 aborption may be less than optimal if it is attempted too early. Patients with pernicious anemia also have a histamine-fast achlorhydria and gastric atrophy. The disease appears to have an autoimmune basis and antibodies to intrinsic factor can be demonstrated in the serum of more than half of affected patients. 

Shaw, R.A. and Mantsch, H.H., Multianalyte serum assays from mid-IR spectra of dry films on glass slides, Appl. Spectrosc., 54, 885-889, 2000. 

The first assay (a radioimmunoassay) that measured cTnl used polyclonal anti-cTnl antibodies. The first monoclonal enzyme-linked immunosorbent assay, anti-cTnl antibody-based immunoassay, was described by Bodor and co-workers (1992). Numerous manufacturers have now developed monoclonal antibody-based diagnostic immunoassays for the measurement of cTnl in serum. Assay times range from 5 to 30 minutes. 

G8. Gertz, B. J., Clemens, J. D., Holland, S. D., Yuan, W., and Greenspan, S., Application of a new serum assay for type I collagen cross-linked A-telopeptides Assessment of diurnal changes in bone turnover with and without alendronate treatment. Calcif. Tissue Int. 63,102—106... 

Once conditions for assay and amount of charcoal are selected, they must be kept constant. If conditions are changed (e.g., larger volumes of serum assayed) the charcoal dose must be reselected. Last, as a precaution, we recommend recharacterization of these data at least once each 6 months to assure proper use. It is important to note that errors in separation of antibody-bound from free ligand are interpreted in the assay as hormone being measured in the assay tube. Such errors in separation can even show parallel dose-response curves between unknown sample and reference preparation. 

This soluble enzyme is specially abundant in skeletal muscle, only one quarter as plentiful in the myocardium and brain, and practically absent from other tissues (C13), so that hemolysis does not affect its activity in serum in the study of muscle disease this distribution offers great advantages. Its function is specifically the equilibration of creatine phosphate and ADP with creatine and ATP, with equilibrium heavily in favor of the latter compounds. Since its activity in serum is some million times lower than in skeletal muscle, serum assay offers certain difficulties three reliable methods, however, are available. 

Proctor KA, Rao LV, RobertsWL Gadolinium magnetic resonance contrast agents produce analytic interference in multiple serum assays. Am J Clin Pathol 121 282-292, 2004. 

Note The protein slide was also tested for other body fluids (e.g. punctates). The results obtained were comparably as good as those obtained by serum assays (E251, E340). 

E9 Kennard, K.C. (1978). New integral analytical element for serum assay. Introduction. Abstracts of Xth Int. Congr. Clin. Chem., Mexico, p. 13, Abstr. 

C3 levels are low in newborns, then rise and remain relatively constant after the first year of life. The recommended reference interval for adults, based on CRM 470, is 0.9 to 1.8 g/L (90 to 180mg/dL). Levels are slightly lower in fresh serum (assayed less than 8 hours after drawing). 

Cummins and co-workers were the first to develop a radioimmunoassay to measure cTnl that used polyclonal anti-cTnl antibodies. Although the assay showed approximately 2% cross-reactivity with skeletal Tnl, it stiU had excellent clinical specificity for cardiac muscle injury. The assay was never automated or developed for commercial use. The first monoclonal ELISA, anti-cTnl antibody-based immunoassay, was described by Bodor et al. This assay has less than 0.1% cross-reactivity with skeletal Tnl, but it was not suited for clinical use because of the lengthy assay time. Over the past 15 years, numerous manufacturers have described the development of monoclonal antibody-based diagnostic immunoassays for the measurement of cTnl in serum. Assay times range from 5 to 30 minutes. As shown in Table 44-1, over a dozen assays have been approved by the FDA for patient testing within the United States on central laboratory and POCT platforms. In addition to these quan-... 

Garnero P, Borel O, Delmas PD. Evaluation of a fully automated serum assay for C-terminal cross-linking telopeptide of type I collagen in osteoporosis. Clin Chem 2001 47 694-702. 

Representative values of total cortisol (free and bound) in serum assayed by immunoassay are as follows ... 

Lentjes EG. Free cortisol in serum assayed by temper-ature-controEed ultrafiltration before fluorescence polarization immunoassay. Clin Chem 1993 39 2518-21. 

Ratdilfe WA. Direct (non-extraction) serum assays for steroids. In Hunter WM, Corrie JET, eds. Immunoassays for clinical chemistry. Edinburgh Churchill Livingstone, 1983 401-9. 

Subsequently, there is a decrease in urinary excretion of the vitamin, which in mrn is followed by diminished tissue concentrations of the vitamin. The most common measurements of vitamin status are assays of circulating amounts in plasma or serum. Assays of biochemical or metabolic function of the vitamin are more likely to reflect body stores than are serum concentrations. Most of these functional assays use erythrocyte or leukocyte extracts to determine apoenzyme activity, which is dependent on the vitamin coenzyme (see Table 135-9). 

Fig. 1. Stimulation of protein synthesis (A) and inhibition of protein degradation (B) over a 4-hour period in L6 myoblasts by IGF-I and IGF-II prepared in the author s laboratory. The dashed hne indicates stimulation of protein synthesis by 10% fetal calf serum. Assays performed by F. J. Ballard and L. C. Read, using published methods (B5).

The two predominant formats used in ILFST are the sandwich and competitive reaction schemes (12). These can be best explained graphically as shown in Fig. 2. The test strip for human chorionic gonadotropin (hCG) is a typical sandwich assay, and those for drugs of abuse are competitive or inhibition assays. In serum assays, specific antibodies are detected as an indicator of... 

A review of the synthesis and chemistry of nitroxide spin labels includes a number of steroid derivatives. Novel spin-labelled steroids have been prepared by esterification with the nitroxyl carboxylic acid derivative (17),for use in spin immunoassays (SIA) as an alternative to radioactive labelling. The prednisolone ester (18), for example, exhibits an e.s.r. spectrum with narrow lines when it is in a free state in solution, but when bound to antibody the rate of tumbling is reduced, and linewidths are broad. Signals from bound and unbound derivatives are easily distinguished and measured, so SIA of antibody-bound prednisolone provides a potentially useful serum assay method. 

Thompson, M. B., and D. J. Kunze. 1984. Polyethylene glycol-6000 as a clearing agent for lipemic serum samples from dogs and the effects on 13 serum assays. American Journal of Veterinary Research 45 2154—2157. 

Tg belongs to the most difficult of serum assays in current routine diagnostics because, of inhomogeneity in the large Tg molecule, where various isoforms of Tg exist with differences in both primary structure and iodine and carbohydrate content. In addition, the presence of circulating autoantibodies against Tg may substantially interfere with the determination of serum Tg. 

---