Biomedical subjects

K L Nuttall

Publications and source records attributed to K L Nuttall.

24 records · Page 2Linked to original sources

PubMedDate not supplied

Effect of storage on serum vitamin B12 and folate stability.

To facilitate transport from remote locations, the stability of vitamin B12 and folate was investigated in serum specimens. Serum vitamin B12 proved to be highly unstable, emphasizing that specimens should be frozen if not analyzed immediately. Light protection is necessary if the sample cannot be analyzed within 4 hours. In contrast, folate is a more robust analyte. In refrigerated serum specimens, folate was stable up to 7 days of storage. In situations where specimen stability is important, vitamin B12 status is better assessed with serum or urine methylmalonic acid measurements. Although folate status can be assessed in a similar fashion with homocysteine, specimen stability indicates that direct measurement of folate is a better strategy.

Blood Preservation↗

PubMedDate not supplied

Orotic acid in clinical urine specimens by capillary zone electrophoresis using polyvinyl alcohol coated capillaries.

Orotic acid is an important compound in the investigation of several inherited metabolic diseases, and capillary zone electrophoresis provides an effective assay method for this analyte in the clinical laboratory setting. Capillaries with a polyvinyl alcohol (PVA) coating performed well in this application. However, it was necessary to employ several specimen preparation steps to achieve good assay precision.

Electrophoresis, Capillary↗

PubMedDate not supplied

Serum methylmalonic acid by capillary zone electrophoresis using electrokinetic injection and indirect photometric detection.

Elevated methylmalonic acid (MMA) is a superior marker for cobalamin (vitamin B12) deficiency. A rapid assay for serum MMA suitable for clinical specimens has been developed. The specimen is injected electrokinetically after a simple extraction. MMA is measured using indirect photometric detection at 210 nm, based on the displacement of phthalic acid in the running electrolyte; no derivatization is needed. The detection limit is 0.2 mumol/L, well below 0.4 mumol/L, which defines elevated concentrations. The assay is linear up to 100 mumol/L, although specimens above 10 mumol/L are diluted to maximize resolution. The CV is < 10% at 0.30 mumol/L and 0.80 mumol/L. The assay gives results that are comparable to more traditional methods.

Biomarkers↗

PubMedDate not supplied

Suspected lead poisoning in a public school.

Reports of lead exposure can generate considerable public concern, particularly when children are involved. In December, 1996, a public elementary school in rural Utah was found to have elevated concentrations of lead in its drinking water. The local public health department responded by instituting remediation of the water supply and by warning parents of the possible danger to their children. Subsequent blood lead testing in 116 of the approximately 300 children involved showed an average lead concentration in the range expected for the U.S. population at large. One of the 116 specimens was marginally elevated and was probably unrelated to the school drinking water. Reducing lead exposure is an important public health concern which sometimes generates a response out of proportion to the danger involved.

Adolescent↗

PubMedDate not supplied

The incidence of elevations in urine 5-hydroxyindoleacetic acid.

A 24-hour urine collection for 5-hydroxyindoleacetic acid (HIAA) is commonly performed to evaluate patients with suspected carcinoid syndrome. However, carcinoids are rare, and elevated results are common even when using an analytically specific method. To characterize this problem, the incidence of elevated results was examined in a population of 947 patient specimens received in a clinical reference laboratory setting. Using a reference limit of 15 mg/d identified 7.9 percent of the results as elevated, with 3 percent > 100 mg/d, and about 1 percent > 350 mg/d. Males showed 14 percent > 15 mg/d compared to 5.2 percent for females. Characterization of incomplete and excess 24-hr urine collections is facilitated by use of a creatinine ratio, with a reference limit of 14 mg/g creatinine equivalent to 15 mg/d. Given the frequency of elevated results, HIAA should be used to support the diagnoses of carcinoid only when consistent with other objective findings.

Adolescent↗

PubMedDate not supplied

Delayed separation and the plasma amino acids arginine and ornithine.

When collecting blood for amino acid testing, leaving plasma in contact with cells at room temperature lowers the concentration of arginine and raises that of ornithine. This is presumably due to the arginase content of red blood cells. In contrast, the sum of arginine and ornithine is constant over the first hour, and defines a reference interval of 74-148 mumol/L (mean +/- 2 SD, n = 20) which is more insensitive to delayed separation. The ratio of arginine to the sum of arginine plus ornithine [arg/(arg + orn)] can be used to estimate the number of specimens not separated promptly. A ratio of 0.74-0.50 (mean +/- 2 SD, n = 20) is characteristic of specimens placed on ice and separated promptly, where delayed separation produces lower ratios. Of 91 adult specimens received for plasma amino acid analysis over five months, 35 (38 percent) showed a ratio < 0.50 suggestive of delayed processing.

Adult↗