DevonSUMMARY IgM rheumatoid factor was assayed by three routine methods: latex fixation; haemagglutination; and end point laser nephelometry in 69 patients with definite or classical rheumatoid arthritis and 58 patients with other non-rheumatoid arthropathies, selected prospectively according to the American Rheumatism Association clinical criteria. The operators of the assays were unaware of the clinical diagnoses. In the group with rheumatoid arthritis 75-4% were positive by latex fixation, 73*9% by haemagglutination, and 55 1% by nephelometry. In the group with nonrheumatoid arthropathies 10-4% were positive by latex fixation, 8-6% by haemagglutination, and 10-4% by nephelometry. Thus the simple and inexpensive latex fixation test was as good as the haemagglutination test, and both were significantly better than nephelometry in the laboratory confirmation of the clinical diagnosis of definite or classic rheumatoid arthritis (X2 = 5.40 and 4 56, and p < 0 025 and < 0 05, respectively). None of these tests was significantly better or worse than the others in producing positive results in the group with non-rheumatoid arthropathies.

Abstract. A method is described for obtaining hepatitis‐associated antigen (HAA) from the acid citrate dextrose plasma of routine blood donations found to be HAA‐positive. The separation consisted of the following steps: ammonium sulphate precipitation, absorption on and elution from DEAE‐Sephadex, and gel filtration on a Sepharose‐6B column. HAA was demonstrated by cross‐over immuno‐electrophoresis and lines of identity shown by the Ouchterlony double diffusion technique. Freedom from contaminating protein was shown by immuno‐electrophoresis. This material, when injected into rabbits, produced an anti‐HAA reagent suitable for use cross‐over immuno‐electrophoresis without absorption.

A simple modification of Hepatest (Wellcome Reagents) is described, which lends itself to the rapid large-scale screening of blood donors. The technique uses 4 ul of HBsAb coated turkey cells , and Terasaki plates (Hopkins and Das, 1973), in contrast to the 25 ,ul used in the microtitre tray technique.This results in a considerable saving on the cost of reagents, the cost per test being reduced to 16% of the cost of the recommended method. In our hands, this modification is as convenient to use as the manual microtitre tray technique.Positive sera from the screen test are also tested for non-specificity using horse IgG coated turkey control cells. The false positive screen test rate has been reduced by the adoption of a modified buffer containing turkey serum. MaterialsHepatest kit (Wellcome Reagents) Terasaki plates and inclined plate stand SMI Micropettor (Dynatech) Oxford dispenser Hamilton repeating dispenser (V. A. Howe) Calibrated Pasteur dropping pipettes-0025 ml (a) Stock buffer 0-1 M Na2HPO4 12H20 35-8 g/l (solution A) 0-1 M NaH2PO4 2H20 15-6 g/l (solution B) Solutions A and B are mixed together in proportions to produce a solution of pH 7-0 (100 ml of solution A + 92 ml of solution B). To this is added an equal volume of 0 15 M NaCl. (b) Buffers for use-prepared fresh daily i Original formula-stock buffer + 5% human group AB serum (HBsAg free), and 2% horse serum (HS02 Wellcome Reagents). ii Modified formula-stock buffer + 4% human group AB serum (HBsAg free), 2 % horse serum (HS02 Wellcome Reagents), and 2% pooled turkey serum.

A simple micro haemagglutination inhibition technique, based on Hepatest (Wellcome Reagents Limited), is described. Its application in the screening of blood donors is shown, and its sensitivity is discussed in two forms of usage and also when compared to the previous immunoelectroosmophoresis technique used in this centre.

suMMARY During a 12-month period, 40 146 blood donors were tested for the presence of high titre antitetanus antibodies. An attempt has been made to define the most suitable donors, those with antitetanus antibody titres of 4 IU/ml or above, by virtue of titre, sex, location, and length of time since most recent immunisation. Particular note is made of those donors from university sessions. Towards the end of the series, donors who had an initially acceptable level of antitetanus antibody were being tested a second time.Sensitisation of recipients to horse immunoglobulin, resulting in hypersensitivity reactions, has led to an increase in the use of human antitetanus immunoglobulin for prophylaxis (Smith et al., 1975). The average yield of antitetanus immunoglobulin is 4 5 g/ litre of crude plasma (Maycock, 1976), and only plasma with an antitetanus antibody level of 3 IU/ml or above is suitable for processing. Bearing in mind the presence of anticoagulant in the blood packs, we therefore set the minimum acceptable level in donor serum at 4 IU/ml. To meet the national need for this product, large-scale blood donor screening has been instituted. Initial experience with the immunoelectroosmopheresis (IEOP) screening test shows that the most useful donors are recently boosted persons, although an acceptable volume of suitable plasma can be obtained by large-scale routine donor screening. Material and methodsAntitetanus antibody is detected and quantitated by a modification of the IEOP screening technique originally used for hepatitis B surface antigen/ antibody detection, developed by Milne and Barr (1971).The buffer system and Agarose plates are used in a similar manner to that originally described, with the exception that only two sets of 30 wells plus control wells are punched into the Agarose (18 ml per plate)