Midland County program provides alternative to mandatory assignment.
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Biomedical subjects
D H Lo
Publications and source records attributed to D H Lo.
Assessment of the fundamental accuracy of the Jendrassik-Gróf total and direct bilirubin assays.
Using unconjugated bilirubin (Bu) and authentic human disconjugated bilirubin (dBc) supplemented in low-bilirubin serum pools, we have directly verified for the first time that the Jendrassik-Gróf total bilirubin assay modified after Doumas et al. (Clin. Chem. 19: 984-993, 1973) detects Bu and dBc quantitatively, in Bu-equivalent concentrations relative to gravimetric concentration assignment reinforced with quantification by nuclear magnetic resonance (Wu et al., Clin. Chem. 26: 1323-1335, 1980). By contrast, the Jendrassik-Gróf direct bilirubin assay (also modified after Doumas) quantifies only 70 +/- 5% of the gravimetrically determined dBc as Bu equivalents. By using Bu and dBc (instead of Bu only, as is routinely done) to calibrate the responses of the total and direct bilirubin assays, the analyses of Bu and dBc become much more quantitative. We mathematically explored the meanings of the conventional terms total, direct, and indirect bilirubins. The clinical and diagnostic implications of our observations are discussed.
Bilirubin↗
The Kodak Ektachem clinical chemistry slide for measurement of bilirubin in newborns: principles and performance.
In this slide, unconjugated bilirubin and its sugar conjugates interact with a cationic polymeric mordant to form spectrally enhanced complexes having similar absorptivities at approximately 400 nm. With reflection densitometry and appropriate mathematical transformation, readings at this wavelength are linearly related to bilirubin concentrations up to 260 mg/L. The slide requires 10 microL of serum, is precise (total CV less than 2% determined over 20 days for the analyte range 39-184 mg/L), gives results that correlate well with the Doumas et al. modification of the Jendrassik-Gróf method (slope 0.95, intercept 0.3, Sy . x 3.4, r = 0.991), and is relatively interference free. Also, the slide measures less loss of bilirubin after in vitro illumination of serum specimens than do diazo tests. An intermediate layer in the slide minimizes the spectral interference from hemoglobin and prevents the detection of the strongly protein-linked ("delta") bilirubin found in many jaundiced adults. The method is recommended for newborns (less than or equal to 14 days), in whom the incidence of delta bilirubin is negligible.
Autoanalysis↗
Automated approach to radioimmunoassays of somatotropin (human growth hormone) and insulin.
The adaptation of human somatotropin and insulin assays to the automated Centria radioimmunoassay system [Clin. Chem. 21, 1305 (1975)] is reported. For the somatotropin assay, reaction conditions include a borate/bovine serum albumin buffer (pH 8.4) AND 20-H Incubation at 4 degrees C. Assay results for clinical samples compared favorably (correlation coefficient = 0.930) with values obtained from a reference laboratory. The means determined for 92 patients' samples were 4.3 mug/liter (reference laboratory) and 5.1 mug/liter (Centria). Intra- and inter-run precision ranged from 3.2 to 15.9%. For the insulin assay, a phosphate/bovine serum albumin buffer (pH 7.4) is used, with a 20-h incubation at 4 degrees C. Previously analyzed insulin samples from a reference laboratory were determined by the Centria analyzer with excellent correlation (r = 0.965). Means for patients' samples were 43.0 milli (USP) units of insulin per liter (reference laboratory) and 47.5 milliunits of insulin per liter (Centria). In both assays an anionicexchange gel is used in the separation step. The criterion of parallelism, an indication of the validity of a radioimmunoassay, was satisfied in both assays. The Centria radioimmunoassay system offers the advantage of automating all the critical steps of these radioimmunoassays.
Autoanalysis↗