Percutaneous conchotome muscle biopsy. A useful diagnostic and assessment tool

To evaluate the diagnostic yield, performance simplicity, and safety of the percutaneous conchotome muscle biopsy technique for clinical and research purposes in an outpatient rheumatology clinic.

Biopsies taken by rheumatologists in an outpatient clinic during 1996 and 1997 were evaluated for histopathological and clinical diagnoses.

A total of 149 biopsies were performed on 122 patients. Physicians learned the method easily. Samples were of adequate size and quality to allow for diagnostics. In total 106 biopsies were taken due to different diagnostic suspicions: 24 polymyositis (PM) or dermatomyositis (DM); 43 PM, DM, or vasculitis in addition to another rheumatic condition; 19 systemic vasculitis; and 20 myalgias. Criteria for definite or probable PM/DM were fulfilled in 21 patients, 18 with positive biopsies. Thirteen patients received vasculitis as clinical diagnosis, 3 with positive biopsies. No patient with myalgia had a biopsy with inflammatory changes. Fifteen of 43 rebiopsies performed to assess disease activity had signs of active inflammation. In 48% there were changes in immunosuppressive therapy after biopsy results. Four complications occurred; one was a serious subfascial hematoma.

The percutaneous conchotome muscle biopsy technique gives a good size sample that allows for diagnostic evaluation and has a high yield in patients with myositis. It is a simple procedure, easy to learn and to perform, with a low complication rate and minimum discomfort for the patient. The method can preferably be used as a diagnostic tool and to perform repeated biopsies to assess the effect of a given therapy for both clinical and research purposes.