OBJECTIVES: Idiopathic normal pressure hydrocephalus (INPH) is characterized by gait impairment and mobility, dementia, and urinary incontinence. Tap test may help to identify which patients with suspected INPH could benefit from shunt surgery. This study aims to evaluate the cost-utility of the Tap test for the insurance plans (private) health perspective.

METHODS: A decision tree model was constructed according to the Brazilian insurance Health perspective. The Tap test accuracy (sensitivity:70%, specificity:50%) and costs (U$229.67); the utilities for shunt success (0.71); the utilities for living with INPH (0.57); direct shunt costs (U$1,670.52), probabilities of shunt success (65%) and death related to shunt (6%) were included as the model parameters. Tap test accuracy and the success rate of shunting was obtained from a rapid literature review. Quality-of-life data were taken before and after six months after the shunt surgery in patients with INPH and of an average age of 70 years from Sweden. Deterministic and probabilistic sensitivity analysis and cost-effectiveness acceptability curves were performed considering an acceptable variation of the parameters’ values.

RESULTS: Tap test may help to avoid around 9% of unnecessary shunt surgery in patients with suspected INPH. The incremental cost-effectiveness ratio (ICER) for the Tap test versus no Tap test was estimated at U$2,222.36/QALY. The probability of shunt success, shunt costs and the utilities associated with a successful shunt were the parameters that most affected ICER, reaching a maximum of U$ 17,888/QALY. The cost-effectiveness acceptability curves identified a 50% probability of the Tap test being cost-effective with a willingness to pay of U$ 5,660/QALY, an amount close to 1 GDP per capita in Brazil.

CONCLUSIONS: Tap test to predict benefit from shunt surgery in patients with INPH may be considered cost-effective in Brazil.