A microtitre plate radioimmunoassay for the detection and semiquantitation of housedust mite, rye grass pollen and cow's milk specific IgG antibodies.

A microtitre plate based radioimmunoassay (RIA) to measure semiquantitatively allergen specific IgA antibodies is described, with optimal coupling conditions for 3 allergens, house dust mite (Dermatophagoides pternoyssinus), rye grass pollen and cow's milk, and the optimal serum and [125I]anti-IgA incubation conditions.

The misuse of buprenorphine and a buprenorphine-naloxone combination in Wellington, New Zealand.

Two surveys of 12 months duration were undertaken on opioid users presenting to the Wellington Alcohol and Drug Centre before and after the introduction of a combination buprenorphine 0.2 mg-naloxone 0.17 mg tablet (Bu-Nx), which was launched in 1991 in the hope of reducing intravenous misuse. There was considerable intravenous (i.v.) misuse of buprenorphine 0.2 mg tablets (Bu) in 1990 with self-reports of misuse in 81% of the patients over the 4 weeks prior to presentation, and 65% of the patients had buprenorphine in their urine. In the repeat survey 57% reported misuse of the Bu-Nx combination over the previous 4 weeks, and 43% had buprenorphine +/- naloxone detected in their urine. There was a reduction in the street price of Bu-Nx. One-third of the patients who used Bu-Nx i.v. reported instances of withdrawal symptoms, and subjectively the drug was less attractive to misusers. The combination product may have less misuse potential than buprenorphine alone, but it remains a preparation, in the dosages employed, that is intravenously misused.

A method for the separation of delta bilirubin using Cibacron Blue affinity chromatography.

We developed and evaluated a method for the separation of delta bilirubin (B delta) by micro-column affinity chromatography based on Cibacron Blue 3G-A-Agarose. Untreated serum was applied to affinity columns and free non-protein bound bilirubins were eluted with phosphate buffer containing 20 g/l Triton X-100. Retained albumin was eluted using caffeine-benzoate reagent and bilirubin associated with this fraction (B delta) quantitated by the method of Jendrassik and Gróf modified by Doumas et al (Clin Chem 1985;31:1779-1789); results correlated well with the high performance liquid chromatography (HPLC) method (n = 35, y (affinity) = 1.009x (HPLC)-5.49; r = 0.959) described by Lauff et al. (J Chromatography 1981;226:391-402). Two controls analyzed with each batch gave between-batch imprecision less than 4.0% (n = 10; Control 1, mean = 20.05 mumol/l; Control 2, mean = 74.82 mumol/l). Within-batch imprecision was less than 3.3% for both levels. Specimens collected from 25 neonates less than 20 days of age showed a B delta concentration of 1.7 +/- 0.7 mumol/l (mean +/- 1 S.D.) and percent B delta of 2.2 +/- 1.9 (mean total bilirubin +/- 1 S.D. = 118 +/- 79 mumol/l). Although time consuming, this simple and precise method allows the measurement of B delta in laboratories without the need for specialized instruments.

Measurement of nicotine in hair by reversed-phase high-performance liquid chromatography with electrochemical detection.

We have developed an assay for nicotine in hair based on reversed-phase HPLC with electrochemical detection. The method uses a low-metal, high-purity silica reversed-phase column. We have investigated the washing, digestion and extraction procedures and discuss the important points in the HPLC method development. The assay is presented as an application in a population of exposed and non-exposed children. Analytical parameters are satisfactory with linearity, recoveries, limit of quantitation and precision all suitable for epidemiological studies involving environmental tobacco smoke exposure assessment.

Specific IgA and IgE in childhood asthma, eczema and food allergy.

Allergen-specific IgA and IgE antibodies were compared in 250 children with asthma (Dermatophagoides pteronyssinus, rye grass pollen), in eighty-six children with eczema (whole egg, cow's milk) and in two groups of children with egg and cow's milk allergy. In each of the conditions investigated, food allergy, asthma and eczema increasing atopy was associated with increasing specific IgE levels to relevant allergens. There was no association of high IgE antibody levels with low IgA antibody levels in any of the conditions or allergens studied. There was, however, a tendency for subjects with more severe asthma to have high IgA levels with high IgE levels. IgA deficiency does not appear to be associated with atopic conditions of childhood.