Osteomalacia associated with anticonvulsant drug therapy in mentally retarded children.

A survey of 289 severely retarded inpatients at a school for retarded children in American Fork; Utah revealed 67 patients with osteomalacia as defined by hypocalcemia, hypophosphatemia, elevated serum alkaline phosphatase levels, and appropriate bone changes. Investigation of the variables which might influence bone mineralization revealed no differences in age, sex, physical activity, sunshine exposure, or dietary intake of vitamin D between the osteomalacia and nonosteomalacia groups. However, all of the patients with osteomalacia were receiving anticonvulsant medications, either phenobarbital, diphenylhydantoin, or both. Duration of anticonvulsant therapy was the most important contributing factor to the development of osteomalacia. Seventy-five percent of patients who had received anticonvulsants for more than ten years had osteomalacia. The single most costly medical problem at the school is the treatment of pathologic bone fractures due to demineralized bone.

Quality control in the office laboratory.

Assuring quality of testing is as important in the doctor's office laboratory as it is in the hospital and independent laboratory. However, the office laboratory's problems and needs are different from those of the larger lab, and the professional laboratorian's solutions are not always appropriate for the office laboratory. It is necessary to recognize that the education and skill levels of the office laboratory staff preclude some of the quality control methods used in professionally staffed laboratories. For some test systems, new control methods will need to be developed. The professional laboratorian can provide valuable assistance to the doctor's office laboratory in assuring quality.

The laboratory evaluation of osteopenia.

Osteopenia is being increasingly recognized as an important cause of morbidity and mortality, and as the cause of a massive health care expense. This realization, and a much greater understanding of mineral and bone metabolism, has resulted in an increase in the sophistication of diagnostic methods. The clinician faced with the problem of osteopenia can rely on the laboratory to facilitate the evaluation of the state of mineral metabolism and, when necessary, to assess the character of bone remodelling.

Assessing an office chemistry instrument.

Selection of appropriate testing systems depends on the characteristics and needs of the office. Clinical practice needs, work flow needs, and the analyst's ability must be balanced against the level of system complexity, automation, quality characteristics, and cost.

An evaluation of a whole blood prothrombin analyzer designed for use by individuals without formal laboratory training.

BACKGROUND: The prothrombin time (PT) test, which is the most common coagulation test used in the outpatient setting, has not been recommended for office laboratory use because it has been technically difficult to perform. Consequently, serious errors in patient care could occur because of an erroneous result. The Coumatrak (E.I. Du Pont, Wilmington, Del) now allows nontechnically trained office staff to perform PT tests using a fresh capillary whole blood sample, individually packaged reagent cartridges, and a portable battery-operated instrument. METHODS: Coumatrak PT testing was compared with standard methods for both precision and accuracy, using protocols developed by the National Committee for Clinical Laboratory Standards (NCCLS). Reagent stability and operator variability were also studied. RESULTS: The results produced by a trained technologist and nontechnically trained staff were comparable. Test results obtained with the Coumatrak were approximately 10% higher than results obtained using standard laboratory equipment and methods using comparable blood samples from the same patients. It was found that the capillary blood specimen had to be rapidly transferred to the reagent cartridge in order to avoid factitiously low results. CONCLUSIONS: The Coumatrak can rapidly provide PT test results that are clinically useful for the office management of patients being treated with a warfarin anticoagulant and for the diagnosis of selected disorders. The system was found to be easy to operate, appropriate for use by individuals with little laboratory experience, and was subject to few operational problems during this study.

Limitations of quality control in physicians' offices and other decentralized testing situations: the challenge to develop new methods of test validation.

Traditional quality-control methods are effective for detecting systematic error caused by deterioration of reagents or instruments, but ineffective for detecting sporadic error, which is more likely to occur in low-volume testing environments. Decentralized testing performed by individuals without formal laboratory training has a high potential for sporadic errors. New methods for validating test results, used each time a test result is produced, should replace current quality-control procedures. Under the rules of CLIA '88, manufacturers and the US Food and Drug Administration have an opportunity to develop new approaches to test validation.

A survey of state regulation of testing for drugs of abuse outside of licensed (accredited) clinical laboratories.

We surveyed all 50 states to find out if testing for drugs of abuse outside of clinical laboratories was regulated. In 14 states such regulations existed or were contemplated. Eight additional states indicated that regulatory language does not restrict their oversight of such testing. Content of the regulations is described for each of these 22 states.

Treatment of hypoparathyroidism and pseudohypoparathyroidism with metabolites of vitamin D: evidence for impaired conversion of 25-hydroxyvitamin D to 1 alpha,25-dihydroxyvitamin D.

In hypoparathyroidism and pseudohypoparathyroidism, pharmacologic doses of vitamin D correct hypocalcemia, but the mechanism is unknown. In two children with hypoparathyroidism and one with pseudohypoparathyroidism we tested the hypothesis that in these conditions there is a defect in synthesis of 1 alpha,25-dihydroxyvitamin D3, the principal active metabolite of vitamin D. In both conditions, minute doses of the metabolite (0.04 to 0.08 mug per kilogram of body weight per day) quickly corrected hypocalcemia and increased intestinal calcium absorption. On the other hand, the effective dose of 25-hydroxyvitamin D3 to maintain normocalcemia was 3 to 4 mug per kilogram per day in the two conditions. Thus, the dosage ratio of 25-hydroxyvitamin D3 to 1 alpha,25-dihydroxyvitamin D3 approximated 100:1. By contrast this ratio was approximately 3:1 in two infants with vitamin D deficiency, a condition in which optimal metabolism of vitamin D would be expected. These findings suggest an impaired conversion of 25-hydroxyvitamin D to 1 alpha,25-dihydroxyvitamin D in both hypoparathyroidism and pseudohypoparathyroidism.