Diagnostic accuracy of CSF tap-test parameters in predicting shunt responsiveness in normal pressure hydrocephalus: a cohort study
10 affiliations
- 1Department of Medicine, All India Institute of Medical Sciences
- 2Department of Clinical Neurological Sciences, University of Western Ontario
- 3Department of Biomedical Sciences, Humanitas University
- 4Department of Neurology, Fixel Institute for Neurological Diseases, University of Florida
- 5Department of Neuroimaging and Interventional Neuroradiology, All India Institute of Medical Sciences
- 6Clinical Research Unit, All India Institute of Medical Sciences
- 7Department of Neurology, All India Institute of Medical Sciences
- 8Department of Neurosurgery, All India Institute of Medical Sciences
- 9Department of Neurology, National Institute of Mental Health and Neurosciences
- 10Movement Disorders Program, Institute of Neurosciences
Abstract
Background The cerebrospinal fluid tap test (CSF-TT) is widely used as an ancillary test to select patients with idiopathic normal pressure hydrocephalus (iNPH) for ventriculoperitoneal (VP) shunt surgery; however, its diagnostic utility remains unclear. Objectives To evaluate the diagnostic utility of CSF-TT in predicting outcomes following VP shunts. Methods Patients with probable iNPH underwent assessments of gait, urinary, and cognitive function using the Dutch gait scale, timed up and go (TUG) gait score, iNPH grading scale, and modified Rankin Scale (mRS) at baseline and 24 h after CSF-TT. They were offered VP shunt surgery based on the clinico-radiological profile, regardless of CSF-TT outcome. Postoperative outcomes were evaluated at 24 weeks, and patients who showed ≥ 1-point improvement in mRS were classified as shunt responders. We also assessed the diagnostic accuracy of the tap test for predicting ≥ 1-point improvement in iNPH at 24 weeks. The diagnostic performance of various baseline tests was assessed using the area under receiver operating characteristic curves (AUROCs). Results 24 patients underwent VP shunting, 15 (62.5%) were classified as shunt responders. A one-point reduction in the mRS at 24 h post-CSF-TT had a sensitivity of 53.3% (95% CI: 26.6–78.7) and specificity of 66.7% (95% CI: 29.9–92.5) in predicting shunt responsiveness based on mRS as outcome. A one-point reduction in the iNPH scale at 24 h post CSF-TT had a sensitivity of 64.3% (95%CI 35.1–87.2) and a specificity of 66.7% (95% CI 22.3–95.7) to predict a one-point improvement in the iNPH scale at 24 weeks post VP shunt. Changes in mRS, Dutch gait score, TUG test score, and iNPH score were not valid predictors, as the confidence intervals of the AUROCs crossed 0.5. Conclusion CSF-TT parameters show limited accuracy in predicting shunt responsiveness in patients with iNPH. Our results suggest that about one-third of positive tap tests were false positives, and the test has poor diagnostic performance as a standalone predictor of postoperative shunt outcomes.
Related
- Accuracy of CSF tap test and lumbar infusion test in predicting shunt response in idiopathic normal pressure hydrocephalus: a systematic review and meta-analysis
- Association between admission serum potassium and quantitative external lumbar drainage responsiveness in patients with hydrocephalus: a retrospective study
- Diagnostic and Predictive CSF Biomarkers in Idiopathic Normal Pressure Hydrocephalus (iNPH): A Systematic Review
- Diagnostic accuracy of Mycobacterium tuberculosis antigen-induced interferon-γ-inducible protein 10 for latent tuberculosis infection among high-risk groups: a systematic review and meta-analysis
- Does visual attention to diagnostic facial features predict eyewitness identification accuracy? Implications for diagnostic feature detection theory
BibTeX
@article{poudel2026diagnostic,
title = {{Diagnostic accuracy of CSF tap-test parameters in predicting shunt responsiveness in normal pressure hydrocephalus: a cohort study}},
author = {Sagar Poudel and Deepa Dash and Alfonso Fasano and Aparna Wagle Shukla and Ajay Garg and Ashish Datt Upadhyay and Naveet Wig and Roopa Rajan and Animesh Das and Divya M Radhakrishnan and Manjari Tripathi and Achal K. Srivastava and SS Kale and P Sarat Chandra and Ashish Suri and Pramod K Pal and Hrishikesh Kumar and Sakoon Saggu and Deepti Vibha and Rajesh Kumar Singh and Jasmine Parihar and Ranveer Singh Jadon and Ved Prakash Meena and Bindu Prakash and Arunmozhimaran Elavarasi},
journal = {BMC Neurology},
year = {2026},
month = jul,
doi = {10.1186/s12883-026-05151-6},
url = {https://doi.org/10.1186/s12883-026-05151-6},
note = {CC BY},
}
RIS
TY - JOUR
TI - Diagnostic accuracy of CSF tap-test parameters in predicting shunt responsiveness in normal pressure hydrocephalus: a cohort study
AU - Sagar Poudel
AU - Deepa Dash
AU - Alfonso Fasano
AU - Aparna Wagle Shukla
AU - Ajay Garg
AU - Ashish Datt Upadhyay
AU - Naveet Wig
AU - Roopa Rajan
AU - Animesh Das
AU - Divya M Radhakrishnan
AU - Manjari Tripathi
AU - Achal K. Srivastava
AU - SS Kale
AU - P Sarat Chandra
AU - Ashish Suri
AU - Pramod K Pal
AU - Hrishikesh Kumar
AU - Sakoon Saggu
AU - Deepti Vibha
AU - Rajesh Kumar Singh
AU - Jasmine Parihar
AU - Ranveer Singh Jadon
AU - Ved Prakash Meena
AU - Bindu Prakash
AU - Arunmozhimaran Elavarasi
PY - 2026
DA - 2026/07/01
JO - BMC Neurology
DO - 10.1186/s12883-026-05151-6
UR - https://doi.org/10.1186/s12883-026-05151-6
AB - Background The cerebrospinal fluid tap test (CSF-TT) is widely used as an ancillary test to select patients with idiopathic normal pressure hydrocephalus (iNPH) for ventriculoperitoneal (VP) shunt surgery; however, its diagnostic utility remains unclear. Objectives To evaluate the diagnostic utility of CSF-TT in predicting outcomes following VP shunts. Methods Patients with probable iNPH underwent assessments of gait, urinary, and cognitive function using the Dutch gait scale, timed up and go (TUG) gait score, iNPH grading scale, and modified Rankin Scale (mRS) at baseline and 24 h after CSF-TT. They were offered VP shunt surgery based on the clinico-radiological profile, regardless of CSF-TT outcome. Postoperative outcomes were evaluated at 24 weeks, and patients who showed ≥ 1-point improvement in mRS were classified as shunt responders. We also assessed the diagnostic accuracy of the tap test for predicting ≥ 1-point improvement in iNPH at 24 weeks. The diagnostic performance of various baseline tests was assessed using the area under receiver operating characteristic curves (AUROCs). Results 24 patients underwent VP shunting, 15 (62.5%) were classified as shunt responders. A one-point reduction in the mRS at 24 h post-CSF-TT had a sensitivity of 53.3% (95% CI: 26.6–78.7) and specificity of 66.7% (95% CI: 29.9–92.5) in predicting shunt responsiveness based on mRS as outcome. A one-point reduction in the iNPH scale at 24 h post CSF-TT had a sensitivity of 64.3% (95%CI 35.1–87.2) and a specificity of 66.7% (95% CI 22.3–95.7) to predict a one-point improvement in the iNPH scale at 24 weeks post VP shunt. Changes in mRS, Dutch gait score, TUG test score, and iNPH score were not valid predictors, as the confidence intervals of the AUROCs crossed 0.5. Conclusion CSF-TT parameters show limited accuracy in predicting shunt responsiveness in patients with iNPH. Our results suggest that about one-third of positive tap tests were false positives, and the test has poor diagnostic performance as a standalone predictor of postoperative shunt outcomes.
SN - 1471-2377
ER -