The diagnosis of polyarteritis nodosa

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Abstract
We evaluated our literature-based estimates of diagnostic test characteristics and aggressive and conservative strategies for the diagnosis of polyarteritis nodosa (PAN) by reviewing 1980 through 1985 data from the University of Chicago Medical Center, Michael Reese Hospital, and Northwestern University Medical School. Test specificity was calculated by reviewing pathology and radiology reports on all relevant procedures done at the University of Chicago Medical Center in 1984 and 1985. There were no reports of false-positive findings (including angiography); thus, test specificity was 100% for muscle, nerve, kidney, liver, and testicular biopsy, which was comparable with our literature-based estimate of 97%. Test sensitivity was based on the 18 confirmed cases of PAN from the 3 institutions and was similar to that in published reports, ranging from 0% for liver biopsy to 100% for visceral angiography. Review of each case for diagnostic test sequence showed an average of 2 diagnostic procedures to confirm the diagnosis (range 1–6). Eight of 18 patients were evaluated according to the conservative strategy we proposed from our literature-based decision analysis approach. No patient was evaluated with the aggressive strategy, although 1 patient had 6 invasive procedures. Of the remaining 10 patients, 9 represented cases that might have been confirmed had the conservative approach been used, and if it had been used, 6 patients would have had the diagnosis confirmed. Thus, the minimum sensitivity of our conservative strategy is 78%, although based on these data, it could be as high as 100%. Our findings suggest that an effective diagnostic approach to the patient with suspected PAN is first serologic and biochemical evaluation, followed by electromyography and nerve conduction velocity to localize symptomatic muscle and nerve involvement. Invasive testing should include muscle and/or nerve biopsy for those with symptomatic sites; if these show negative findings, visceral angiography should be performed. If there is no symptomatic site, visceral angiography should be performed; if the findings are negative, blind muscle biopsy should be performed. Testicular biopsy should be considered if the patient is symptomatic, although there are presently too few data about this procedure to recommend it without qualification. This conservative strategy appears to maximize the accuracy and minimize the cost and morbidity of the investigation.

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