BACKGROUND AND PURPOSE:

• Saramago et al. (BJOG, 2018) evaluated the cost-effectiveness of high-throughput, non-invasive prenatal testing (HT-NIPT) for fetal Rhesus D (RhD) genotype to guide antenatal prophylaxis with anti-D immunoglobulin compared with routine antenatal anti-D immunoglobulin prophylaxis (RAADP)
• This study was devised to inform NICE recommendations

METHODS:

• Cost-effectiveness decision-analytic modeling
  • A decision tree model was used to characterize the antenatal care pathway in England and the long-term consequences of sensitization events
• The diagnostic accuracy of HT-NIPT was derived from relevant literature sources and databases
• HT‐NIPT is assumed to be introduced early enough in the care pathway to guide the use of anti-D immunoglobulin at 28 weeks of gestation
• For women with false‐negative HT‐NIPT results who receive only postpartum anti‐D immunoglobulin, the model assumes a rate of sensitization of 0.95%
• HT-NIPT is considered highly accurate (treating inconclusive result as positive)
  • Sensitivity: 0.998
  • Specificity 0.942

Five alternative strategies measuring the impact HT-NIPT would have on existing postpartum care were considered

• Current practice
  • Postpartum cord serology for all; fetal-maternal hemorrhage testing as necessary and anti-D immunoglobulin based on fetal-maternal hemorrhage results
• HT-NIPT Strategy 1
  • Any HT-NIPT RhD result: Postpartum cord serology; fetal-maternal hemorrhage testing and anti-D immunoglobulin as appropriate
• HT-NIPT Strategy 2
  • Negative result treated as diagnostic (potential for false negatives)
  • Positive or inconclusive confirmed with cord blood serology
• HT-NIPT Strategy 3
  • RhD-negative result requires confirmation
  • Positive (including inconclusive) treated as diagnostic (potential to overtreat false positives)
• HT-NIPT Strategy 4
  • All NIPT results treated as diagnostic, with inconclusive treated as positive
• HT-NIPT Strategy 5
  • NIPT negative requires cord blood confirmation
  • NIPT positive does not require cord blood confirmation
  • Inconclusive requires cord blood confirmation

RESULTS:

• HT-NIPT is highly accurate and appears to be economical, but also less effective than current practice, irrespective of the postpartum strategy evaluated
  • Authors found the “magnitude of the potential cost‐savings appeared sufficient to outweigh the small increase in sensitisations and the associated small QALY loss”
• A postpartum strategy in which inconclusive test results are distinguished from positive results lead to the best performance (Strategy 5)
• The cost-effectiveness of HT-NIPT is dependent on the overall test cost being less than or equal to £26.60

CONCLUSION:

• HT-NIPT could reduce unnecessary treatment with routine anti-D immunoglobulin and is cost saving compared to current practice
• Authors point out an important limitation – data on the diagnostic accuracy of HT-NIPT among non-white ethnicity is lacking and this group of pregnant women may have more inconclusive test results

Learn More – Primary Sources:

High‐throughput, non‐invasive prenatal testing for fetal Rhesus D genotype to guide antenatal prophylaxis with anti‐D immunoglobulin: a cost‐effectiveness analysis

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