Antibody Titres and Two Types of Bias

Abstract

Statisticians have pointed out that when antibody titres are determined using the standard definition (see Sect. 2.1.2), the reciprocal of the highest dilution at which the assay read-out did occur, the true titre value is underestimated [23]. This is easy to see. By definition, the true antibody titre τ lies between the standard titre t _s and the reciprocal of the next dilution, r _n :

$${t}_{s} \leq \tau < {r}_{n}.$$

Thus, for most serum samples the standard antibody titre will be lower than the true titre. This means that if standard antibody titres are used, the geometric mean titre will underestimate the geometric mean of the distribution underlying the antibody values.

There are antibody assays that try to correct for this bias.