A rapid polyethylene glycol assay for gastric intrinsic factor

The use of polyethylene glycol (mol. wt 4000) in a rapid radioassay for intrinsic factor is reported. The assay is based on the observation that polyethylene glycol precipitates the intrinsic factor-vitamin B12 complex in the presence of serum from patients with pernicious anaemia having auto-antibodies against intrinsic factor. The assay was found highly reproducible (CV 1.8%) and well correlated to the classical method using coated charcoal in the separation step.