Use of a computer to evaluate sigmoidal curves in serology by a new procedure

Serological standard curves are mostly sigmoidal in shape. Their transformation into straight lines by linear regression can be the source of serious error. Log/log or logit/log handling of the values can straighten the curve but only if their distribution is normal. A new way of calculating concentrations of antibody or antigen which leaves the standard curve unmanipulated is described. Computer programs for TI 59 (Texas Instruments) and--in BASIC--for a personal computer have been written and greatly facilitate routine work.