BONE ALKALINE-PHOSPHATASE IN RHEUMATIC DISEASES

A double monoclonal immunoradiometric assay specific for bone alkaline phosphatase (BAP) was used to determine whether the raised total alka line phosphatase (TAP) often found in patients with active rheumatoid arthritis (RA) and ankylosing spondylitis (AS) is derived from bone or liver. Fifty-eight patients with RA were compared to 14 with AS and 1 4 with non-inflammatory rheumatic diseases (NI). None had clinical liv er disease and only one had a slightly elevated aspartate transaminase activity. Elevated BAP concentrations were found in seven patients (5 RA, 1 AS, 1 NI), only two of whom also had abnormal TAP. Abnormal TAP activities were found in only three patients (all RA). BAP did not co rrelate with disease activity in RA or AS. In contrast, TAP correlated with disease activity (assessed by plasma viscosity) in RA (P < 0.02) and AS (P < 0.002) and gamma-glutamyl transferase (GGT) also correlat ed with plasma viscosity in RA (P < 0.01). Both TAP and BAP were signi ficantly correlated with GGT in RA (P < 0.001 and P < 0.02, respective ly). These findings are discussed, together with possible reasons for the conflicting nature of some of the observations.