Laboratory tests for detection of human immunodeficiency virus type 1 infection.
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Acquired Immunodeficiency Syndrome↗
Biomedical subjects
N F Nuwayhid
Publications and source records attributed to N F Nuwayhid.
Digoxin elimination in a functionally anephric patient after digoxin-specific Fab fragment therapy.
The elimination of total digoxin after digoxin-specific Fab fragment therapy in a patient in end-stage renal disease is described. Two-component, nonlinear exponential regression of the patient's total digoxin concentration data revealed biphasic elimination: a fast phase with a half-life of 43 h and a slow phase with a half-life of 330 h. Serum total digoxin concentration decreased 20% 12 h after the initiation of Fab fragment therapy. The mean serum concentrations of total digoxin and apparent total digoxin as measured by fluorescence polarization immunoassay during a 520-h period after the initiation of therapy were 18.42 and 14.77 ng/ml, respectively (n = 15). The correlation between the two measurements was good (r = 0.987). The time course of free digoxin concentration obtained after ultrafiltration at 2, 20, or 37 degrees C is also described. The free digoxin concentrations (n = 10) at these temperatures averaged over a 282-h period were 0.35, 0.53, and 0.82 ng/ml, respectively (p less than 0.001, 2 degrees C vs. 37 degrees C).
Aged↗
Multipoint kinetic method for simultaneously measuring the combined concentrations of acetoacetate-beta-hydroxybutyrate and lactate-pyruvate.
This is a multipoint kinetic method for simultaneously determining acetoacetate (AcAc) plus beta-hydroxybutyrate and lactate plus pyruvate in a single cuvette of the Multistat III centrifugal analyzer. In the first step, AcAc and pyruvate are completely reduced, using 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30) and lactate dehydrogenase (EC 1.1.1.27) in the presence of excess NADH at pH 7.5, to beta-hydroxybutyrate and lactate, respectively. After dilution, the endogenous beta-hydroxybutyrate and lactate and that resulting from reduction are simultaneously oxidized by their respective dehydrogenases in the presence of excess NAD+ at pH 9.0. Adjustment of the relative enzyme concentrations allows simultaneous estimation of AcAc plus beta-hydroxybutyrate and lactate plus pyruvate by analyzing multipoint absorbance data, collected during the oxidation reaction, with use of a two-component linear-regression model. Total run-to-run CVs were 6.4% and 6.1% at 5 mmol/L beta-hydroxybutyrate and 5 mmol/L lactate, respectively. The method was designed to be useful for identifying the cause of an increased anion gap in serum.
3-Hydroxybutyric Acid↗
Kinetic measurement of the combined concentrations of acetoacetate and beta-hydroxybutyrate in serum.
This is an automated method for the kinetic measurement of the combined concentrations of acetoacetate and beta-hydroxybutyrate in a single channel of the "Multistat III" centrifugal analyzer. Acetoacetate is first reduced with high concentrations of NADH by catalysis with 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30). This reaction mixture is diluted with excess NAD+. The endogenous beta-hydroxybutyrate and that resulting from acetoacetate are then measured kinetically. Comparing the combined concentration of acetoacetate and beta-hydroxybutyrate (y) with the sum of acetoacetate and beta-hydroxybutyrate measured as described by Hansen and Freier (Clin Chem 1978;24:475) (x) yielded the relationship: y = 0.99x - 0.57 (r = 0.93, n = 25). The run-to-run CVs for low (5 mmol/L) and high (15 mmol/L) acetoacetate controls were 12% and 6%, respectively. The method is useful for determining the concentration of ketone bodies in 2-microL samples of serum of patients with diabetic ketoacidosis. The sensitivity can be increased to determine ketone body concentration in nonketotic individuals by increasing sample volume to 10 microL.
3-Hydroxybutyric Acid↗
Quantification of analyte and interferent by multipoint analysis.
We have investigated the application of multipoint kinetic curve-fitting methods to the determination of an analyte in the presence of a single interferent. Our model system for the analyte-interferent was creatinine-acetoacetate as determined with the kinetic Jaffé method. We examined the utility of the following multipoint approaches: simultaneous equations, multivariable linear regression, and iterative multivariable nonlinear regression. With appropriate restrictions, all approaches could detect acetoacetate interference and quantify both creatinine and acetoacetate. A two-stage linear regression approach was both versatile and computationally simple. Interferent was detected in the first stage, and both analyte and interferent were quantified in the second stage if the interferent was assumed known and an adequate fit of the model to the data was obtained. Using the two-stage linear regression model, we obtained results for 10 ketotic patients that correlated well with results by enzymatic methods for creatinine (r = 0.976) and acetoacetate (r = 0.995); we also demonstrated that creatinine could be quantified in the presence of the antibiotic cefoxitin.
Acetoacetates↗