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. 2020 Nov 2;20(15):1–160.

Table 21:

Probabilistic Sensitivity Analysis Scenarios: Changes in Structural and Parameter Assumptions

Parameter/Assumption: Population of Interest Reference Case Analysis Scenario Analysis: Major Changes in Parameter Values or Assumptions
Inclusion of paternal phenotyping: both populations Maternal testing only: intervention with noninvasive fetal RhD genotyping Paternal RhD testing, assuming patient consent; paternal testing included in both strategies (intervention and usual care)
Probability of inconclusive results after genotyping: both populations 0.067 (0.004)37,39 2% to 10%37
Test accuracy: both populations Sn: 99.7%; Sp: 96.1% 39 Sn: 99.7%; Sp: 98.7% (see Table 15)39
Probability of alloimmunization: nonalloimmunized population only    
  • RhIG at 28 weeks and birth 0.00262 0.0031 (95% CI 0.0021 – 0.0040)57
  • RhIG after birth only 0.01662 0.0067 (95% CI 0.0050 – 0.0084)57
  • No RhIG 0.12 0.166,11
Compliance with testing and RhIG: nonalloimmunized population only    
  • Fetal RhD genotyping 100% Assumed 0.78 for the scenario analysis, based on the range reported in our clinical review: 0.78 to 0.93 (Clausen et al, 201489)
  • RhIG 100% Probability of receiving universal prophylaxis at 28 weeks and birth: 0.99 (Soothill et al, 201549; Saramago et al, 201837)
Probability of receiving RhIG after a potentially alloimmunization event: 0.958 (0.006)37
Analysis perspective: alloimmunized population only Ministry of Health perspective Societal perspective
Cost of noninvasive RhD fetal genotyping: both populations Estimated (Table 17) Estimated, provided by OOC-PA Program (Table 22)
Lower cost: nonalloimmunized pregnancies (Table 22)
Cost of cord blood sampling: both populations Procedure cost: $772 (SE: $24) (Tables 18 and 19) Lab fee cost solely: $6.81 (Tables 18 and 19)
Probability of long-term neurodevelopmental problems: alloimmunized population only 0.048 (SE: 0.003)93 3 times smaller than reference case estimate
Long-term costs and HSUs of the state associated with major developmental problems: alloimmunized population only HSUs and costs, combined for major developmental problems and cerebral palsy (see Table 16 and Table 20): HSUs = 0.4237 and 0.3087 Scenario A assumed:

  • HSUs of major developmental problems in general: 0.42 (SE: 0.03)37

  • Costs of major developmental issues in general (costs of cerebral palsy excluded)


Scenario B assumed:

  • HSUs of major developmental problems in general: 0.42 (SE: 0.03)37

  • Twice-lower costs of major developmental issues (costs of cerebral palsy excluded)


Scenario C assumed:

  • HSUs of major developmental problems in general: 0.42 (SE: 0.03)37

  • 10-times higher costs of major developmental issues (costs of cerebral palsy excluded)


Scenario D assumed:

  • HSUs of major developmental problems of 0.67 (SE:0.03),87 based on upper-end HSUs for people with cerebral palsy

  • Twice-lower the reference case cost estimate (including Ontario's estimates for costs of cerebral palsy)
Discount rate: both populations 1.5% 5%
Time horizon: both populations Long-term: 10 years Shorter: 1 year, 5 years, and lifetime
Multiple pregnancies: nonalloimmunized population only Nonalloimmunized population only, one pregnancy Approximation, time horizon: 10 years and lifetime

2 pregnancies: first nonalloimmunized pregnancy followed by either a nonalloimmunized or alloimmunized pregnancy

Abbreviations: CI, confidence interval; HSU, health state utilities; NA, not applicable; OOC-PA Program, Out-of-Country Prior Approval Program; RhD, rhesus D blood group; RhIG, Rh immunoglobulin; SE, standard error; Sn, sensitivity; Sp, specificity.