Serum testosterone measurement in men: Evaluation of modern immunoassay technologies

Figures & data

Table I.  Main analytical characteristics, as defined by manufacturers of five non-isotopic and one isotopic testosterone immunoassays.

Manufacturer	Vitros ECi (Ortho-Clinical Diagnostics)	Architect (Abbott Laboratories)	Access (Beckman Coulter)	Delfia (Perkin-Elmer)	DRG International Inc	RIA WHO matched reagent program
Immunoassay principle	Competition	Competition	Competition	Competition	Competition	Competition
Antibody nature	M-at biotinylated	M-at	M-at	P-at IgG	M-at	M-at
Solid phase	SA-coated wells	Coated paramagnetic particles	Coated paramagnetic  particles	Anti-rabbit IgG	M-at	–
Labeled testosterone	Horseradish peroxidase	AE	AP	Eu^3 +	Horseradish peroxidase	^3H
Detection	ICL	DCL	Luminescence	Fluorescence	Absorption	β-emission
Sample volume μL	25	150	20	25	25	50
Total incubation time (min)	32	29	20	125	75	50
Calibration stability days	28	28	14	Run to run	Run to run	Run to run
Analytical measurement range (nmol/L)	0.3–73.6	0–52	0.3–48	0–65	0–55.5	0–33
Detection limit (nmol/L)	0.03	0.28	0.3	0.3	0.24	0.3
Within-assay CV (%)	2.5 (52.7)	1.9 (17.5)	3.9 (1.05)	6 (2.4)	5.8 (3.4)	8.8 (2.8)
	3.1 (2.01)	4.5 (2.84)	2.14 (25.05)	5.5 (10.2)	3.8 (18.9)	6.5 (14.2)
Between-assay CV (%)	4.9 (52.7)	3.7 (17.5)	7.1 (1.05)	12.9 (12.9)	3.7 (3.4)	11.2 (3.1)
	7.0 (2.01)	8.0 (2.84)	4.9 (25.05)	6.8 (10.2)	3.0 (19.2)	9.6 (14.4)
Expected values (adult men)	4.6–28.2	9.7–38.14	5.25–23.4	9.4–33.5	8.3–41.6	12–35

Table II.  Testosterone concentration in serum samples from 100 men obtained by RIA and five non-isotopic methods.

	Geometric mean	Median	Minimum	Maximum	SD	Wilcoxon matched-pairs test, p-level
Access	13.9	14.2	3.1	50.1	6.8	0.000000 (RIA/Access)
Delfia	19.3	19.2	3.6	94.6	13.0	0.000000 (RIA/Delfia)
Architect	16.8	17.8	3.8	114.4	12.7	0.000000 (RIA/Architect)
DRG	15.6	16.3	3.5	40.8	6.5	0.000000 (RIA/DRG)
Vitros ECi	12.7	13.1	1.8	44.2	7.7	0.019009 (RIA/Vitros ECi)
RIA	12.1	13.0	2.1	34.6	6.0	–

Table III.  Mean differences in T concentrations between RIA and tested immunoassays.

	n	Median (nmol/L)	Range	SD
Access–RIA	100	1.23	−7.00–41.30	4.90
Delfia–RIA	100	7.25	−10.40–85.80	11.80
Architect–RIA	100	4.90	−7.30–105.60	11.30
DRG–RIA	100	2.70	−9.80–19.00	4.10
Vitros–RIA	100	0.40	−5.20–16.80	4.20

Table IV.  Differences (%) in testosterone concentrations obtained by 5 non-isotopic methods and by RIA.

	T concentrations over range, median (range)	RIA T < 10 nmol/L Subgroup 1	RIA T > 10 nmol/L Subgroup 2	P1–2
Access–RIA	12 (−26–+ 469)	29 (−7–+ 469)	0.1 (−26–+ 100)	= 0.000
Delfia–RIA	65 (−61–+ 951)	97 (−14–+ 951)	49 (−61–+ 124)	= 0.000
Architect–RIA	39 (−45–+ 1200)	70 (−44–+ 1200)	34 (−45–+ 190)	= 0.000
DRG–RIA	21 (−33–+ 284)	53 (−5–+ 284)	17 (−33–+ 77)	= 0.000
Vitros–RIA	0.03 (−49–+ 163)	0.04 (−49–+ 163)	0.03 (−34–+ 76)	= 0.920

Figure 1. Percentage differences in testosterone concentrations measured by RIA and non-isotopic methods in two male subgroups, with RIA T < 10 nmol/L and RIA T > 10 nmol/L.

Figure 2. Correlation between total T concentrations (nmol/L) measured by both RIA and Vitros.

Figure 3. Correlation between total T concentrations (nmol/L)measured by RIA, Architect (upper plot) and DRG (lower plot).

Figure 4. Correlation between total T concentrations (nmol/L)measured by RIA, Delfia (upper plot) and Access (lower plot).

Table V.  Comparison between testosterone results obtained using RIA and 5 non-isotopic immunoassays for samples in a subgroup with low testosterone concentrations (RIA T results < 10 nmol/l; n = 32) using regression analysis.

Methods tested	Equation for regression line	Beta coefficient	P =
Access	Access = −2.087 + 1.8084 * RIA	0.459	0.0080
Delfia	Delfia = −8.760 + 3.7201 * RIA	0.392	0.0264
Architect	Architect = −5.200 + 2.7689 * RIA	0.300	0.0950
DRG	DRG = −.5855 + 1.7393 * RIA	0.629	0.0001
Vitros ECi	Vitros = −1.817 + 1.4389 * RIA	0.607	0.0002

Table VI.  Comparison between testosterone results obtained using RIA and 5 non-isotopic immunoassays for samples in a subgroup with high testosterone concentrations (RIA t results > 10 nmol/l; n = 68) using regression analysis.

Method tested	Equation for regression line	Beta coefficient	P =
Access	Access = 3.5612 + 0.84311 * RIA	0.829	0.000
Delfia	Delfia = 6.7199 + 1.0479 * RIA	0.631	0.000
Architect	Architect = 3.8619 + 1.0794 * RIA	0.695	0.000
DRG	DRG = 5.7376 + 0.83149 * RIA	0.743	0.000
Vitros ECi	Vitros = −0.6268 + 1.1220 * RIA	0.794	0.000

Figure 5. Ratio of testosterone concentrations measured by Access, Vitros and RIA in two subgroups of men, with RIA measuring T < 10 nmol/L and T > 10 nmol/L.

Figure 6. Ratio of testosterone concentrations measured by Architect, Delfia and RIA in two male subgroups, with RIA measuring T < 10 nmol/L and T > 10 nmol/L.

Figure 7. Ratio of testosterone concentrations measured by DRG and RIA in two male subgroups, with RIA measuring T < 10 nmol/L and T > 10 nmol/L.