oubie-blinded study of normal indivi

The use of skin test conversion as a measure of change in cellular immune status is a fairly routine procedure despite considerable potential for variation in testing. This study is a double-blinded and randomized reassessment of this assay in the context of transfer factor (TF) activity. Thirty-three normal people with negative tuberculin skin tests received either dialyzable TF, column pur$ed TF, hypoxanthine, or saline in a randomized and double-blinded fashion. Skin test reactivity to tuberculin and keyhole limpet hemocyanin (KLH) was read by three of the investigators. Nine of 20 recipients of TF and 7 of 13 controls demonstrated an increase in tuberculin reactivity after “transfer.” Four reactions were greater than 10 mm. Fourteen of20 recipients of TF and 7 of 13 controls demonstrated some reactivity to KLH on initial testing post-transfer. Control solutions were as effective as TF preparations in “causing” skin test conversion. These observations stress the importance of controlled and blinded studies when serial skin test reactivity is used to evaluate cellular immune status in humans.