Background: Published data imply that adult concentrations are achieved for all Ig isotypes and plateau by 15-18 years of age. Recent data, however, suggest that these results are not applicable in the elderly. There are no equivalent data for IgG subclasses. We present reference range data for an elderly UK patient population, for IgG, IgA, IgM and IgG subclasses.
Methods: Serum immunoglobulins were reviewed on samples from 1146 patients > 60 years of age and 925 patients aged 18-60 years. Serum IgG subclasses were reviewed on samples from 498 patients >60 years and 484 patients aged 18-60 years. All Igs and subclasses were measured by nephelometry. Reference ranges were derived by probability plotting.
Results: Serum median IgG and IgM concentrations are reduced in the elderly (IgG female P < 0.001, IgG male P < 0.03; IgM female P < 0.001, IgM male P < 0.001). Serum IgA concentrations are maintained. Indeed, men showed a slight increase in serum IgA with age (P = 0.03). Few differences dependent on gender were seen. Median IgM was lower in men in the younger age groups (18-60 years P < 0.001; 61-70 years P = 0.017). IgG(2) is reduced in elderly men (P = 0.002) and IgG, reduced in elderly women (P = 0.009).
Conclusions: We advocate that centres offering these investigations provide local, method-dependent reference ranges, and suggest an approach as to how this might be achieved.