Antineutrophil cytoplasmic antibody (cANCA and pANCA) titers in relation to disease activity in patients with necrotizing vasculitis: a longitudinal study.

The significance of the antineutrophil cytoplasmic antibodies, cANCA or pANCA, in relation to disease activity in various types of necrotizing vasculitis was assessed in a longitudinal study. Twenty patients, 14 cANCA positive and 6 pANCA positive were followed for up to seven years. Eleven of the 14 cANCA positive and two out of the 6 pANCA positive patients had Wegener's granulomatosis, two other cANCA patient and one pANCA patient had systemic vasculitis, whereas one cANCA and three pANCA positive patients had disease limited to the kidneys. Disease activity was expressed as a numerical index DAI, based on extent and type of organ involvement (DAI greater than or equal to 5 = active disease). At the time of disease debut the DAI ranged between 11 and 32, cANCA titers between 18 and greater than 1000 U/l, and pANCA titers between 51 and 630 U/l in individual patients. With clinical recovery both c- and pANCA titers declined. Clinical remission (DAI less than 5) occurred within a mean of 2.5 months (range 1 to 4). Almost simultaneously cANCA titers turned negative (less than 10 U/l), although one patient remained positive for seven years. pANCA titers remained positive for long periods of time in 5/6 patients. Five cANCA patients had clinical exacerbations, which in two patients were preceded by seroconversions from - to +, lasting 3 and 12 months before the clinical relapse. One additional cANCA patient had two serological relapses without signs of clinical activity during a 2-year follow-up. In conclusion, we saw a close correlation between DAI and cANCA titers in individual patients: with decreasing clinical activity (DAI), the cANCA titers decrease. Interindividual variation is great; despite a high DAI, the cANCA titers may be relatively low. Serological relapses may indicate forthcoming clinical relapses. Relapses may develop as late as 5-6 years after onset. pANCA titers, on the other hand, tend to remain positive for long periods, despite clinical remission.