Objective: To study the pooled sensitivity and specificity of the CSF tap test and lumbar infusion test.

Background: Idiopathic Normal pressure hydrocephalus is a condition characterized by a specific triad of gait disturbance, cognitive impairment, and urinary incontinence. It affects 0.5 to 2.9 % of elderly patients and is equally common in both sexes. CSF tap test and lumbar infusion test are often done pre-operatively to predict outcomes and used to prognosticate patients regarding the likelihood of improvement following ventriculoperitoneal or lumbo-peritoneal shunt.  Guidelines suggest that they have a higher specificity and lower sensitivity in predicting the outcome and there are controversial opinions regarding their predicting power and validity. The optimum cutoffs and timing of assessment following the tap test to predict the improvement after shunting are not known.

Method: We did a systematic review and meta-analysis to study the sensitivity and specificity of the CSF tap test and lumbar infusion test. The protocol for this review was registered in PROSPERO, with the registration number CRD42023454502.

Results: We identified 1446 studies, removed duplicates, and screened 1049 articles for eligibility as per our inclusion and exclusion criteria. We extracted data from 15 studies that reported the results of the index tests and reference standard. We found there was a lot of clinical heterogeneity in the protocols of lumbar tap test and lumbar infusion tests in various institutions, the timing of assessment, and various scales and cutoffs used in assessing outcomes. Some studies were retrospective and had significant biases. We found the pooled sensitivity of the CSF tap test to be 66.5% (95%CI 49.6-81.6) and pooled specificity 52%(95%CI 35.7-68.1). The pooled sensitivity and specificity of the lumbar infusion test were 76.8%(95%CI 70.3-82.8) and 48.9%(95%CI 18.8-79.4) respectively.

Conclusion: The role of the CSF tap test and lumbar infusion test is modest at best in predicting outcomes following shunt surgery. Both the investigations had a poor pooled specificity of 52% and 49% respectively which is similar to a toss of a coin. Using these investigations to prognosticate patients should be done with these findings in light. We need better predictive models to help select patients for surgery and also help shared decision-making.

Specificity of CSF Tap test

Sensitivity of CSF tap test

Sensitivity of Lumbar Infusion test

Specificity of Lumbar infusion test

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