Abstract: Objective To establish a new protocol and receiver operator characteristic curves of acute levodopa challenge test with consecutive dosage of levodopa in Parkinson disease (PD). Methods The levodopa responsiveness was analyzed in 151 parkinsonian patients, including 102 with a clinical diagnosis of PD and 49 with non-PD parkinsonian syndrome. All patients received consecutive dosage of oral levodopa/benserazide (50/12.5 mg, 100/25 mg, 150/37.5 mg, 200/50 mg, 300/75 mg) every morning in 5 days. The UPDRS part Ⅲ scores were evaluated every 30 min until 6 h after administration. The maximum improvement of UPDRS part Ⅲ scores was compared between patients with PD and those with non-PD. The receiver operating characteristics curves were plotted comparing PD vs non-PD. The cutoff of improvement was defined as the value with maximal diagnostic sensitivity and maximal specificity. Results The sensitivity and specificity of the test were over 80% with selective cut-off point were 150/37.5 mg, 200/50 mg and 300/75 mg of levodopa/benserazide. The sensitivity was 97.1% when the cut-off point was set at 28.5% with 300/75 mg of levodopa/benserazide. The specificity was 93.2% when the cut-off point was set at 22.5% with 150/37.5 mg of levodopa/benserazide. Conclusion The acute levodopa challenge test with consecutive dosage of levodopa/benserazide should be used to assess the levodopa responsiveness. The cutoff of improvements may be useful in diagnosis of PD.

Key words: Parkinson disease, levodopa responsiveness, acute levodopa challenge test, receiver operator characteristic curves