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Appendix D: Cost-effectiveness of intravenous immunoglobulin (IVIG)

Table D.4 Cost–benefit parameters

Parameter Value Source Notes
QALY gain from averted 25 Approximately 75 to 80 years of
exchange transfusion mortality life lived in full health
Willingness to pay for a QALY £20,000 NICE guidelines manual An advisory threshold of
(2009) 237 £20,000 to £30,000 is
suggested in the manual
Discount rate 3.5% NICE guidelines manual
(2009) 237

D.4 Results

The results with base-case values are shown in Tables D.5 and D.6 for Rhesus haemolytic
disease and ABO haemolytic disease, respectively.

Table D.5 Cost-effectiveness of IVIG for babies with Rhesus haemolytic disease with base-case
model values

Treatment Cost Mortality QALY loss ICER
No IVIG £2,108 0.02 0.5 –
IVIG £2,670 0.01 0.25 £2,248 per QALY

Table D.6 Cost-effectiveness of IVIG for babies with ABO haemolytic disease with base case model
values
Treatment Cost Mortality QALY loss ICER
No IVIG £2,108 0.02 0.5 –
IVIG £3,302 0.016 0.4 £11,944 per QALY

With base-case values, IVIG appears to be cost-effective in babies with Rhesus and ABO
haemolytic disease with incremental cost-effectiveness ratios (ICERs) of less than £20,000 per
QALY. The treatment appears to be most cost-effective in babies with Rhesus haemolytic
disease, which is because the data suggest a lower NNT to avoid an exchange transfusion. If
more exchange transfusions are avoided, that has a beneficial effect on both ‘downstream’ costs
and averted mortality.

D.5 Sensitivity analysis

The results for the base-case analysis are only as reliable as the base-case inputs that produce
them. There is important uncertainty in some of these inputs, especially with respect to
exchange transfusion mortality and the NNT to avoid exchange transfusion. The 95%
confidence intervals for the NNT were as follows:
• Rhesus haemolytic disease: 1.6 to 3
• ABO haemolytic disease: 3 to 13
In exploring this uncertainty, there is limited value in exploring scenarios where exchange
transfusion mortality is higher than the base case, the NNT is lower than the base case and the
cost differential between exchange transfusion and IVIG is bigger than the base case. That is not
to say that such scenarios are implausible but rather they would simply reinforce the observed
cost-effectiveness of treatment. Rather, we are more interested in subjecting the cost-effectiveness
finding to scrutiny by observing the extent to which the cost-effectiveness would still hold with
the least propitious but still plausible scenarios. Therefore, the sensitivity analyses take a ‘worst-
case’ scenario with respect to clinical parameters and a threshold approach to costs.

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