Biomedical subjects

M I Clarke

Publications and source records attributed to M I Clarke.

3 recordsLinked to original sources

PubMed1996

Thyroid function testing based on assay of thyroid-stimulating hormone: assessing an algorithm's reliability.

OBJECTIVE: To assess the ability of an algorithm for thyroid-function testing (based on assay of thyroid-stimulating hormone [TSH]) to discern euthyroidism in patients with and without conditions affecting thyroid function. DESIGN: The Australian Health Insurance Commission (HIC) specifies clinical categories for which Medicare rebate is given for assay of both TSH and free thyroxine (FT4), but otherwise rebates for thyroid function testing are given for TSH assay only. A prospective study was made of paired TSH and FT4 results of 1000 consecutive assays categorised by indication for testing. An FT4 value within the reference range was accepted as indicating euthyroidism; the reliability of an initial TSH measurement as the sole indicator of thyroid disease was assessed against this criterion standard. SETTING: A large suburban teaching hospital. OUTCOME MEASURE: Success or failure of the algorithm, with failure defined as an abnormal FT4 level missed because the TSH level was normal. RESULTS: The algorithm failure rate both overall and in the patients not in the HIC clinical categories was 2.7%, and there was no significant difference in algorithm failure rate in the patients in the various HIC clinical categories. The categories and failure rates were: patients being monitored for thyroid disease, 3.4%; patients with the "sick euthyroid" syndrome, nil; patients with psychosis or dementia, 1.1%; patients taking drugs affecting thyroid function, 2.1%; and patients with pituitary dysfunction, one of six cases. The range of FT4 values in patients in whom the algorithm failed was 6.4-29.5 pmol/L in those without thyroid disease and 3.4-27.4 pmol/L in those with thyroid disease. In patients being monitored for thyroid disease, the proportion of abnormal values of TSH alone was significant (P<0.001). CONCLUSION: We have shown that the HIC's imposition of a TSH-based algorithm by financial fiat is also scientifically acceptable. Use of this algorithm in hospitals (including psychiatric hospitals) will result in substantial savings.

Algorithms↗

PubMed1986

Black teenage pregnancy: an obstetrician's viewpoint.

The Black pregnant teen is a microcosm of the impact of society on the most vulnerable. Who is the pregnant adolescent? What racial and ethnic connotations are implied? What is the quality of her progeny? What health risks and mortality attend Black pregnant adolescents? What measures are indicated to address teen pregnancy? Health providers must more intensively address the essentials of the socio-medical phenomenon of Black teenage pregnancy. The United States leads other developed countries of the world by substantial margins in births to teenagers, ranging from 3/1,000 in Japan to 52/1,000 in the United States. In 1983 in New York City, 40,000 teenagers became pregnant resulting in 14,000 births, 20,000 abortions, and 6,000 miscarriages. Sixty-six percent of the births occurred in areas with large concentrations of residents of lower socio-economic status. Special attention, then, needs to be focused on both pregnancy prevention and early prenatal care in these high risk areas. Most teenagers do not intend to become pregnant. There are suggested racial differences regarding both the intention of becoming pregnant and teen births. Twenty percent of pregnant teenagers conceive during the first sexual exposure and fifty percent become pregnant within the first six months. The younger the age at initiation of intercourse, the greater the likelihood of pregnancy. The desire to terminate a teen pregnancy is more closely associated with socio-economic status than ethnicity. The course of pregnancy in teenagers is more likely to be complicated by a variety of clinical problems than in adults. Further, the maternal mortality rate in pregnant black teenagers is significantly higher than in white teenagers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1983

Optimization of pharmacokinetic monitoring: I. Linear pharmacokinetics.

To reach and maintain therapeutic drug concentrations, reliable estimates of the parameters describing the pharmacokinetic behavior of the drug are required. The accuracy and precision of the pharmacokinetic parameters are dependent upon the error associated with the time of specimen collection and the laboratory assay error. In this report, the determinate error and random error are analyzed independently and incorporated in calculations of regimens of two drugs, gentamicin and theophylline. The calculations show that, within a particular concentration range, there are better times for sampling to determine the elimination rate constant and, consequently, the dose. From the generalized, first-order equation for a one-compartment pharmacokinetic model, ln Ct = ln C0 - Kt, where C = plasma drug concentration, t = time, C0 = C at zero time, and the elimination rate constant, K = 0.693/t1/2, the determinate error, epsilon K, in K is epsilon = (1/C0t)epsilon C0 - (In C0/C)t-2 epsilon t, and the random error, assuming a gaussian distribution, is (formula; see text) where S2x is variance of parameter x. Therefore, the variances of the calculated quantity, C0, the measured quantity, C, and the time of sample collection, t, are initially of equal importance. However, with increasing t, the effect of S2t becomes small. In both random and determinate error cases, increased time of sampling after dose reduces the error in K, thus t1/2, as do recognized biological factors. However, increased relative analytical error may obliterate this advantage if analyses are not modified to obtain best quantitation at low, even subtherapeutic concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗