CSF tap test - Obsolete or appropriate test for predicting shunt responsiveness? A systemic review.

Objectives: There is no accurate test for diagnosing normal pressure hydrocephalus or for screening for patients who will benefit from shunt surgery. Additional tests, such as cerebrospinal fluid tap test (CSF-TT), are often used in practice to provide further predictive value in detecting suitable patients for shunting. We performed a systematic review of the literature to evaluate the CSF-TT's effect on the outcome of main symptoms and on validity parameters in screening patients suitable for shunting.

Methods: In February 2015 we searched electronic databases from their inception to the current date, using the following key words: normal pressure hydrocephalus, idiopathic normotensive hydrocephalus, shunt operation, CSF tap test, predictive value, validity. The search retrieved 8 articles explicitly addressing the topic.

Results: There was a very high positive predictive value of CSF-TT: 92% (range from 73% to 100%) but a low negative predictive value: 37% (18%-50%). Also, the CSF-TT has high specificity: 75% (33%-100%) but average sensitivity: 58% (26%-87%). The overall accuracy of the test was 62% (45%-83%).

Conclusions: This systematic review did not provide unambiguous validity of the CSF-TT in the screening of patients for shunting. The validity of the CSF-TT is good for patient inclusion for shunting due to the fact that the positive response to the test is very reliable. Unfortunately, the negative response to the test does not reliably make these patients ineligible for shunting. Further studies are needed to improve and standardize the methodology in order to optimize the detection power of the test.