Plasma gamma glutamyltransferase levels during rifampicin therapy for tuberculosis

A possible effect of rifampicin enzyme induction on microsomally derived plasma gamma glutamyltransferase (gamma GT) during treatment for tuberculosis patients with spinal bone disease and pulmonary or lymph node involvement was studied. Of 10 patients with bone disease 5 had raised levels prior to therapy (greater than 60 IU/l) and none were alcohol consumers. Gamma GT is not known to be present in bone and this probably represents an indirect effect on the liver. Changes in gamma GT in the first 2 months of rifampicin/isoniazid treatment were variable and will not serve as an index of response to therapy. Of 69 patients with lung or lymph node disease 15 had raised levels during treatment and 9 had a high alcohol intake, when the alcohol group were excluded there was no significant difference from controls who had completed treatment (p greater than 0.1). We conclude that plasma gamma GT, a standard clinical estimation of liver dysfunction, is a useful index of suspicion for alcoholics among the tuberculous group but the disease itself can produce similar levels. It did not reflect the known hepatic microsomal inducing properties of rifampicin and thus differs from the anticonvulsant model. Clinical value would be enhanced if specific liver isoenzymes in plasma were identified which separated tissue injury, enzyme induction and the effect of extrahepatic infection on the liver.