SHBG on Testosterone Recovery. Testosterone,g/L ... Our data, which are in agreement with Masters and Hfihnel (1) and ... Los Angeles, CA 90045. Association ...
usually diminished. Therefore the SHBG effect is of minor importance in the measurement of T. Nevertheless, this problem can be overcome by doveloping adequate SHBG-dissociating agents for no-extraction assays, because practical reasons argue against the use of extraction assays for T. References 1. Masters AM, HShnel R. Investigation of sex-hormonebinding globulin interference in direct radioimmunoassays for testosterone and estradiol. Clin Chem 1989;35:979-84. 2. Luppa P, Langmandel U, Neumeier D, Knedel M. Beeinfiussung der TestosteronMessung durch das Sexual-Hormon-bindende Globulin in Radioinununoassays ohne Extraktion. Fresenius Z Anal Chem 1988;330:400-1. 3. SlaMs EH, Kennedy JC, Kruijswijk H. Interference of sex-hormonebinding globulin in the “Coat-A-Count” testosterone no-extraction radioimmunoassay. Clin Chem 1987;33:300-2. P. Luppa
D. Neumeier of Clin. Chem. Univ. of Munich Marchioninistr. 15 D-8000 Munich 70, F.R.G.
kit was reformulated over a year ago and that since June 1988 this assay no longer has a significant SHBG interference up to the highest concentration tested, i.e., 180 nmol/L. Table 1 documents the absence of such an SHBG effect and should correct any remaining false impressions. SHBG calibrators obtained from the Diagnostic Products Irma-Count SHBG kit were each supplemented to contain an additional 4.2 pg of testosterone per liter. Recoveries of testosterone are based on differences between the results before and after this supplementation.
this
References
1. Masters AM, H#{224}hnel R. Investigation of sex-hormonebinding globulin interference in direct radioimmunoassaysfor testosteroneand estradiol.Clin Chem 1989;35:97984. 2. Slants EH, Kennedy JC, Kruijswijk H. Interference of sex-hormonebinding glob. ulm in the “Coat-A-Count” testosterone no-extraction radiounmunoassay. Clin Chem 1987;33:300-2.
Instit.
0
5
IC
t3-HIT.utostson.
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20
25
Peter Bodlaender Technical Director Diagnostic Products Corp. 5700 West 96th Street Los Angeles, CA 90045
No SHBG interference with the “Coat-A-Count Total Testosterone” Direct RIA Kit
Association between Paracetamol and Pyrogiutamic Aciduria
(nmol/L)
Fig. 1. Effectof SHBG on analyticalrecovery of T in radioimmunoassays with (top) and without(bottom) extraction in two sera with high (253 nmol/L, -u- -) and low (10 nmol/L, -A-) content of SHBG -
lutions give parallel curves for T for both pooled sera. Counts of the tritiated T were identical in both cases (data not shown). Our data, which are in agreement with Masters and Hfihnel (1) and also with Slaats et al. (3), clearly verify that SHBG strongly influences the equilibrium adjustment of the binding reaction between ligand and antibody-the most important step in immunometric measurements. Use of the extraction technique totally abolishes the influence of SHBG. The question the clinical chemist must ask in this context is the following: what is the clinical relevance of precise determination of T in serum, especially in the lower range? Doubtless, it is the diagnosis of hyperandrogenism in hirsute women. But it must be considered that, in these patients, concentrations of SHBG in serum are
To the Editor: In their recent article, Masters and Hfihnel (1) reported on sex-hormone binding globulin (SHBG) interference in direct radioimmunoassays for testosterone, and supporting data were provided for the Farmos, Mallinckrodt, and Immuchem kits. Although additional data were not provided, the authors reiterated conclusions previously published by Slaats et al. (2), which identified a similar SHBG interference in Diagnostic Products Corporation’s “Coat-A-Count Total Testosterone” assay. However, Masters and Hfihnel seem to be unaware that
To the Editor: Creer et al. (1) recently described an adult patient with pyroglutamic aciduria in whom an enzyme defect (namely glutathione synthetase or 5-oxoprolinase deficiency) was considered unlikely. They concluded that an unidentified exogenous agent was most likely the cause of the patient’s pyroglutamic aciduria. A routine drug screen showed the presence of paracetamol in the urine of this patient. Another adult patient with pyroglutamic aciduria and normal enzyme activities is also known (case report in
Tabie 1. Effect of SHBG on Testosterone Recovery Testosterone,g/L Sample
SHBG, nmol/L 0.0
Unsuppl.
Suppl.
A
0.00
4.04
Recovered, 96%
B C D E F
1.0 3.0 30 90 180
0.00 0.02 0.14 0.40 0.88
4.34 4.38 4.48 4.65 4.73
103%
%
104%
103% 101% 92%
CLINICAL CHEMISTRY, Vol. 36, No. 1, 1990 173
preparation). This patient had a presentation similar to that of the patient of Creer et al. and was also receiving paracetamol. These reports prompted a fuller investigation of the association between paracetamol and pyroglutamic aciduria. Urine specimens were selected from those submitted for routine metabolic screening. All specimens were analyzed for amino acids by high-voltage paper electrophoresis, with ninhydrin staining. Paracetamol shows a distinct band on staining with ninhydrin, and 10 urines containing paracetamol and a control group with no detectable parseetamol (n = 10) were chosen for further study. The pattern of amino acids was within normal limits in both groups. After extracting and converting to trimethylsilyl derivatives by a standard method (2), urinary pyroglutamic acid and paracetamol were quantified by gas chromatography/mass spectrometry, with selected ion plots. Ions used for the quantifications were 156 m/z for pyroglutamic acid, 223 mlz for paracetamol, and 299 mlz for an internal standard, pentadecanoic acid. Urinary creatinine was measured in a centrifugal analyzer by using a kinetic Jaff#{233} reaction. Figure 1 shows the values for pyroglutaniic acid found in the control group and in the group receiving paracetamol. Although the latter values are lower than in patients with enzyme deficiencies, they significantly exceed those for the control group. Patients who excrete small quantities of pyroglutamic acid have been detected during routine urine metabolic screening and have been associated with artipyroglufamic
acid smol/mmoi
of creatinine
ficial diets (3), ingestion of glutamate (4), and the anticonvulsant drug vigabatrin (5). It is well known that paracetamol can deplete intracellular glutathione reserves, and this might be expected to lead to a transient pyroglutamic aciduria by a mechanism analogous to that operating in glutathione synthetase deficiency. These results support this hypothesis and suggest that paracetamol ingestion is another factor that should be considered in patients undergoing investigations for pyroglutamic aciduria. I thank Mrs. Helen Croll and Mr. Peter Vervaart foramino acid screening and creatmine determinations, andMr. David Rutherford (Alfred Hospital, Melbourne) and Dr. Garry Brown (Dept. of Pediatrics, University of Melbourne) for helpfuldiscussions. References 1. Creer MH, Lau BWC, Jones JD, Chan K. Pyroglutamic acidemia in an adult patient. Clin Chem 1989;35:684-6. 2. Tanaka K, Hine DG, West-Dull A, Lynn TB. Gas-chromatographicmethod of analysis of urinary organic acids I. Retention indices of 155 metabolically important compounds. Clin Chem 1980;26:1839-46. 3. OberholzerVG, Wood CBS, Palmer T, Harrison BM. Increased pyroglutamic acid levels in patients on artificial diets. Clin Chim Acta 1975;62:299-304. 4. Ghezzi P, Garattini S, Caccia S, et al. Plasma pyroglutamic acid levels after oral administration
of monosodium glutamate
to human volunteers. Toxicol Lett 1983; 15:123-9. 5. Bonham
JR, Rattenbury JM, Meeks A, Pollitt RJ. Pyroglutamic aciduria from vigabatrin [Letter]. Lancet 1989; June
24:1452-3.
James
Pitt
Dept. of Clin. Biochem. Royal Children’s Hospital Melbourne, Australia
0
Urinary “Oligocional”
0o 100
Bands in AIDS
C 0 0 0
I0
0
00 parscetamol
000000000
controls
Fig. 1. Urinarypyroglutamicacidexcretionof patientson paracetamolcomparedwithcontrols The two groups differed significantly(P
