Table 2.

Tap test

Study	Shunted patients	Methodology	Criteria for + ve TT	Criteria for SR	Side effects	Main reported outcomes
Shigeki Yamada et al. (2017) [73]	n = 151	• Assessments: TUG time in seconds was measured pre- and within 24-h post-TT. Percentage time improvement = (TUG time before TT minus TUG time after TT or shunt surgery)/TUG time before TT × 100 (%). Simple time difference = TUG time before TT – TUG time after TT or shunt surgery • TT involved ≥ 30 mL removal of CSF • Follow up: 3, 6, and 12 months	• TUG time improvement of ≥ 5 s	• TUG time improvement of ≥ 10 s for clinically sufficient out	• Not reported	• Post-TT: deteriorated (approx. 10% of patients), < 5-s improvement (≥ 50%), ≥ 5- to < 10-s improvement (24%), and ≥ 10-s improvement (13%) • Threshold of 5.6-s threshold predicts a shunt outcome improvement of ≥ 10 s in TUG 12-month post-shunt with sensitivity = 83.3%, specificity = 81.0% • TP = 21, FN = 4, FP = 4, TN = 40
Carsten Wikkelsø et al. (2012) [70]	n = 115	• Assessments: iNPH scale and mRS scale. iNPH Scale score: weighted mean score of assessments in gait, neuropsychology, balance, and continence. iNPH scale range: 0 to 100 (100 = normal performance in healthy people within an age range of 70–74 years) • TT involved 50 mL removal of CSF • Follow up: 12 months	•  + 5% mean increase in motor and psychometric tests values compared to 24 h before	•  + 5 points on iNPH scale • OR − 1 point on mRS	• Not reported	• 84% improved on iNPH scale. 69% improved on mRS scale (35% improved by 1 point, 25% by 2 points, and 7% by 3 points) • Significant correlation between gait tasks improvement (10 m of walking at free speed) with TT and improvement in iNPH score (r = 0.22, p = 0.02) • TT: sensitivity = 52%, specificity = 59%, PPV = 88%, NPV = 18% • TP = 51, FN = 47, FP = 7, TN = 10
Hertel et al. (2003) [24]	n = 15	• Assessments: pre- and post-TT patients were clinically assessed and evaluated using SPECT, pwMRI, neurological examination, walking test, psychometric examination (MMS), the HHS, and incontinence protocol • STT involved 40–50 mL removal of CSF • Follow up: 3 months	• Improved clinically, or by increasing perfusion in SPECT or pwMRI • − 4-point HHS scale • Imaging: global increase in cerebral blood flow on SPECT and of cerebral blood volume in pwMRI	• Black rating scale for shunt assessment: excellent, good, or fair	• Not reported	• 33% of patients had marked clinical improvement post-TT in the HHS and positive imaging (all shunted). 33%; TT negative or questionable but positive imaging (6 received a shunt). 33%; no clinical improvement nor positive imaging (not shunted) • At TT, there was a highly significant association between clinical assessment and perfusion changes (p < 0.01, w = 0.5) • No significant difference was found between HHS scores (7.94, positive group; 7.22, negative group) • No difference was found in CSF pressure values between positive and negative TT groups • TP = 8, FN = 5, FP = 1, TN = 1
Walter et al. (2005) [66]	n = 14	• Assessments: pre- and post-shunt: neurological exam, walking test, psychometric examination (MMS), HHS, and urinary incontinence protocol • STT involved 40–50 mL removal of CSF + MRI assessment • Only those who improve following STT (either clinically or increased perfusion in PWI-MRI) had shunt • Follow up: 6 months	• Minimum – 4 points on HHS scale • Walking test: step number reduction or 10% increase in average pace length	• Black rating scale for shunt assessment: excellent, good, or fair	• Not reported	• 25% of patients demonstrated increased cerebral perfusion and clinical improvement post-TT. 32% of patients demonstrated increased cerebral perfusion, but no significant change in clinical assessment. 46% of patients demonstrated neither a change in cerebral perfusion nor clinical assessment • 57% of patients had improved cerebral perfusion after STT • There was a significant difference between clinical assessment and perfusion changes (p < 0.01, effective size (w) = 0.63) • In the “improved” group, the pre-STT baseline perfusion values were significantly lower than the “no improvement” group. Significant increases from pre- to post-STT were only found in the “improved” group • STT: sensitivity = 50%, specificity = 50% • TP = 6, FN = 6, FP = 1, TN = 1
Ishikawa et al. (2012) [26]	n = 100	• Assessments: iNPHGS, MMSE, and the 3 m TUG. Post-shunt: mRS. Secondary outcome measures: iNPHGS, MMSE, and TUG as secondary outcome measures • TT involved ≥ 30 mL removal of CSF • Follow up: 3, 6, and 12 months	• iNPHGS: ≥ 1-point improvement • TUG: ≥ 10% improvement in time • MMSE: ≥ 3-point improvement	• mRS: 1 point or more improvement over 12 m	• Not reported	• CSF pressure at TT was significantly higher (p < 0.05) in shunt responders (median = 13 mmHg) than non-responders (median = 12 mmHg) • TT total (improvement in iNPHGS or MMSE or TUG): sensitivity = 92.5%, specificity = 20% • iNPHGS: total scale improvement: sensitivity = 71.3%, specificity = 65%. GS-gait change: sensitivity = 51.3%, specificity = 80.0%. GS-cognitive change: sensitivity = 25.0%, specificity = 85.0%. GS-urinary continence change: sensitivity = 37.5%, specificity = 85.0% • TUG: sensitivity = 34.2%, specificity = 73.6% • MMSE: sensitivity = 63.8%, specificity = 30% • GS total change and CSFP ≥ 15 cm H2O: sensitivity = 82.5%, specificity = 65.0% • TP = 74, FN = 6, FP = 16, TN = 4
Ishikawa et al. (2016) [27]	n = 61	• Assessments: TUG, 10Ti (10-m walk in time), and the 10St (10-m walk in steps) pre-TT and on days 1 and 4 post-TT • TT involved 30 mL of CSF drainage • Follow-up: 3 months	• iNPHGS: ≥ 1-point improvement or ≥ 10% improvement in TT quantitative measures	•  ≥ 1-point improvement on the grading scale	• Not reported	• TUG day 1 post-TT: sensitivity = 78.3%, specificity = 80% TUG day 4 post-TT: sensitivity = 73.2%, specificity = 50.0% • 10Ti day 1 post-TT: sensitivity = 63.0%, specificity = 66.6% 10Ti day 4 post-TT: sensitivity = 63.4%, specificity = 90.0% • 10St day 1 post-TT: sensitivity = 41.3%, specificity = 86.7% 10St day 4 post-TT: sensitivity = 41.5%, specificity = 80.0% • TUG and 10Ti times significantly decreased (ANOVA: TUG p = 0.044; 10Ti p = 0.015) from pre-TT to day 1 post-TT and from pre-TT to day 4 post-TT

Studies included assessing the use of tap test (TT) in predicting shunt responsiveness. SR, shunt response; TUG, timed up and go test; iNPH, idiopathic normal pressure hydrocephalus; mRS, modified Rankin scale; SPECT, single-photon emission computerized tomography; pwMRI, perfusion-weighted imaging MRI; HHS, Homburg hydrocephalus scale; STT, spinal tap test; iNPHGS, iNPH grading scale; 10St, 10-m walk in step test; 10Ti, 10-m walk in time test.