Table 4

Number needed to follow (NNF) of three measures of four devices and a power of >90%

Measure chosenGold standardAcceptable change from gold standardTime point(s) to assess atMaximum
NNF*
Total h ip/ k nee r eplacement
Harris Hip Score/Knee Society ScorePostoperative score at year 24 points or d=0.35 and 10 years341
QoLPreoperative scoreTHR: 1.4, 2.4 points or d=0.3, 0.5
TKR: 1.6, 2.7 points or d=0.3, 0.5
1 year181
RevisionAnnual rate of 0.5%OR=1.55 and 10 years2500
EVAR
EndoleakAnnual rate of 2.8%OR=1.52 and 5 years1400
30-day all-cause mortality2%OR=1.530 days2200
Secondary vascular interventionAnnual rate of 4%OR=1.54 and 6 years450
Surgical mesh for POP
Erosion6%OR=1.51 year800
QoLPreoperative score8.6, 14.4 points or d=0.3, 0.51 year181
Total reoperation rate3%–4%OR=1.51 year1500
  • The gold standard for continuous outcomes is based on a baseline measure (before surgery or 2 years after surgery) and that for binary outcomes is based on gold standard rates from literature or expert opinion.

  • *The maximum is over multiple scenarios of gold standards and time points.

  • EVAR, endovascular aneurysm repair; POP, pelvic organ prolapse; QoL, quality of life;THR, total hip replacement; TKR, total knee replacement; d, Cohen’s d.