Utility of needle muscle biopsy in a university rheumatology practice

To evaluate the utility of percutaneous needle muscle biopsy (NMB) as an alternative to open biopsy for the evaluation of patients with myopathy encountered in a university hospital based rheumatology setting.

Chart review of all patients (n = 30) who underwent NMB at our institution over a 4-year period. Patients were grouped according to clinical outcome. Records of 91 patients who underwent open biopsy during the same period were reviewed for comparison.

NMB results either confirmed or added to the prebiopsy diagnostic suspicion in 11 patients and excluded a low prebiopsy suspicion in 13, thus yielding useful clinical information in 24 of 30 patients (80%). Biopsy left the suspected diagnosis unresolved more frequently in patients undergoing NMB compared to patients who had open biopsy during the same time period (6/30 vs 1/91). In the 6 cases unresolved by NMB, subsequent open biopsy added additional information in only 2 of 5 patients. Sensitivity of NMB for inflammatory myopathy was 83% in the 23 patients suspected of having this disease. NMB could be arranged twice as fast as open biopsy, and provided adequate tissue for evaluation in all cases.

Our results suggest that NMB is an effective tool for obtaining useful diagnostic information, particularly pertaining to the presence of an inflammatory myopathy. The convenience, low morbidity, and sensitivity of NMB make it a procedure worthy of wider application by rheumatologists.