The Validation and Use of Kveim Test Suspensions

Sarcoid spleens removed at operation for valid clinical indications provide the best available source for the provision of continued supplies of potentially satisfactory Kveim test material. Chase-Siltzbach type 1 suspensions (ref. 1) are prepared from deep-frozen splenic tissue either in sequential Lots of approximately 35g each or by processing the whole spleen. The former necessitates the validation of sequential Lots of test material whilst the latter assumes that all parts of the spleen will yield an acceptable test suspension and runs the risk that a portion of the spleen may impair a large volume of a suspension which may otherwise have proved satisfactory. In any event, less than one half of all potentially acceptable sarcoid spleens will provide suspensions which yield the expected proportion of positive reactions among patients at different stages of sarcoidosis and a negligible proportion among patients with other diseases. These acceptable suspensions should comprise fine splenic tissue particles which are evenly dispersible in suspension. The concentration of these tissue particles will usually range between 3.0 mg/ml – 6.0 mg/ml as measured by alcohol precipitable dry weight. The potency and selectivity of test suspensions can be assessed only by validation in man. The reactivity of a suspension is determined by comparison of papule size and histology with that of a simultaneous test using a previously validated suspension in patients with sarcoidosis. The selectivity of a suspension for sarcoidosis is ascertained by comparing the results of identical simultaneous tests in patients with diseases other than sarcoidosis. The histology must be read by an experienced observer who is unaware of the origin of the test suspensions or the nature of the subjects tested. Although test suspensions can usually be kept satisfactorily at +4°C at least for several years, they should be monitored periodically to ensure that they have not lost either their reactivity or selectivity for sarcoidosis. When a large volume of acceptable test material has been prepared it is therefore usual to ampoule and store at +4°C; alternatively, it could be freeze dried when it appears to retain its potency for long periods at room temperature (refs. 2,3,4,5,6,7).