Yves Léonce Mardens

Plasma and urinary cortisol levels after dexamethasone in affective disorders

The validity of the dexamethasone suppression test was evaluated for the differential diagnosis of primary and secondary depressions. Forty hospitalized psychiatric patients (14 primary depressed, 15 secondary depressed and 11 non-depressed controls) were studied. The Research Diagnostic Criteria of Spitzer et al. (1978) were used to classify these patients. Eight out of the 14 primary depressed patients had an abnormally high plasma cortisol at 4 p.m. after dexamethasone. Only 2 out of the 15 secondary depressed patients and none of the 11 controls had an abnormal response to dexamethasone. Based on these results, the dexamethasone suppression test has a sensitivity of 57%, a specificity of 87% and a predictive value of 80%. The determination of urinary free cortisol excretion does not improve the performance of the test.

Comparison of two extraction procedures for urinary organic acids prior to gas chromatography-mass spectrometry

We have compared a new isolation procedure for urinary organic acids using strong anion-exchange columns with a solvent partition (ethyl acetate) method. Urinary samples from two healthy children and from nine children with organic acidurias were analysed by both procedures. Although the solid-phase extraction is more efficient for polyhydroxy acids, some polar acids, and some glycine derivatives, clinically important compounds such as oxalic, methylcitric, pyruvic, glyoxylic and 2-ketoglutaric acids, are not recovered or are only poorly recovered. However, both procedures may be used as a routine method for the diagnosis of the organic acidurias included in this study.

A rapid gas-liquid chromatographic determination of serum levels of phenobarbital and diphenylhydantoin

This report describes a simple gas-liquid chromatographic method for the simultaneous determination of phenobarbital and diphenylhydantoin in serum or plasma. The procedure involves a simple extraction with an isobutylmethyl ketone/n-hexane mixture, on-column ethylation with a methanolic solution of tetraethylammonium hydroxide, and analysis on a flame ionisation chromatograph. This method offers advantages of accuracy, sensitivity and rapidity. No interference from other constituents of blood was found. This reliable technique is well adapted to the routine monitoring of epileptic patients.

Improved gas-liquid chromatographic method for the simultaneous determination of phenobarbital, phenytoin, carbamazepine and primidone in biological fluids

The method proposed here for the simultaneous determination of phenobarbital (PB), phenytoin (DPH), (CBZ) and primidone (PM) in biological samples is an improvement on other published flash-heater methylation methods. The two above-mentioned problems have been solved by the combination of appropriate internal standards (in particular, a new internal standard for CBZ), a modified rapid extraction procedure, and the use of a thermionic detector.

Cross-reactivity assessment of oxcarbazepine and its metabolites in the EMIT assay of carbamazepine plasma levels.

To study the possible cross-reactivity of trans-10, 11-dihydroxy-10, 11-dihydro-carbamazepine (DHCBZ), the diol metabolite of carbamazepine (CBZ), of oxcarbazepine (OCZ), and of its metabolites in the CBZ-enzyme multiplied immunoassay technique (EMIT), this technique was used to analyze sera spiked with CBZ, OCZ, DHCBZ, and 10-hydroxy-10, 11-dihydro-carbamazepine (HCBZ). OCZ and, to a lesser extent, HCBZ cross-reacted with the CBZ-EMIT reagents. However, from a clinical point of view, only HCBZ could significantly interfere in the quantitation of CBZ levels in the plasma of patients taking both CBZ and OCZ. There was no interference by DHCBZ.