Cerebrospinal fluid proteins in meningitis

Oestradiol-178 is the most active oestrogen in premenopausal women. Assays for oestradiol are of value in the investigation of normal and abnormal ovarian function. Rapid oestradiol measurements are effective in monitoring ovulation induction in the treatment of female infertility, and sensitive assays facilitate the detection of lower oestradiol concentrations found in men and postmenopausal women. Oestradiol178 is measured chiefly by radioimmunoassay methods (Barnard et al., 1975). Alternative assays systems have included the use of fluorescent-labelled antibody (Ekeke et al., 1979) and 8-galactosidase conjugated to oestradiol in a competitive enzyme immunoassay (Maurel et al., 1987). We have developed a sensitive, precise, solidphase enzyme immunoassay for oestradiol in serum, using an oestradiol-horseradish peroxidase conjugate. Sheep anti-(oestradiol) antiserum, raised against the 3-carboxymethol ether-bovine serum albumin conjugate, was coated on to microtitre plates. These plates were incubated at 4°C for 12 h, washed, and stored at 4°C before use. Oestradiol-178 in serum was extracted with diethyl ether. Standards, control serum and unknown serum samples (50 P I ) , together with an oestradiol-horseradish peroxidase conjugate, were dispensed into individual wells. After incubation at 4°C for 4 h, the plates were washed again, and bound oestradiol178 detected by the addition of hydrogen peroxide and o-phenylenediamine in citrate phosphate buffer. Sulphuric acid was used to stop the colour reaction, and the absorbance was measured at 492 nm on a microtitre plate reader interfaced to a BBC microcomputer. Fig. 1 shows a composite standard curve for oestradiol178, derived from 10 successive assays. The S.D. values for the BIB, ratios (bound enzyme activity at each standard concentration divided by bound activity at zero standard) for each standard ranged from 0.53 to 3.78, indicating that the precision and stability of the standard curve are satisfactory. The sensitivity of the assay, defined as the standard concentration equivalent to the B, minus 2 S.D. of B,, is 45 pmol/l, which is equivalent to 613 fg/weU. Intraand inter-assay variation for low, medium and high oestradiol-178 control samples, expressed as the mean coefficient of variation, were 3.4, 9.0%; 4.0, 6.4% and 7.0, 8.4%, respectively. The antiserum exhibited a significant cross-reaction with oestrone loo 90 E