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Cherry MG, Greenhalgh J, Osipenko L, et al. The Clinical Effectiveness and Cost-Effectiveness of Primary Stroke Prevention in Children with Sickle Cell Disease: A Systematic Review and Economic Evaluation. Southampton (UK): NIHR Evaluation, Trials and Studies Coordinating Centre (UK); 2012 Nov. (Health Technology Assessment, No. 16.43.)

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The Clinical Effectiveness and Cost-Effectiveness of Primary Stroke Prevention in Children with Sickle Cell Disease: A Systematic Review and Economic Evaluation.

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Appendix 7Calculation of model outputs

Model outputs

Incremental cost

Incremental cost (iC) = CtI − CtC

where:

  • CtI = cost of treatment (intervention)
  • CtC = cost of treatment (non-intervention)

and:

CtI = ∑[SPIbd × (SCb + Tf × TCfg + Gfh × GCh) + NSId × (Tf × TCfg + Gfh × GCh + SSi)]
CtC = ∑[SPCbd × (SCb + Tf × TCfg + Gfh × GCh) + NSCd × (Tf × TCfg + Gfh × GCh + SSi)]

where:

  • SPIbd= number of patients who have had at least one stroke in state b in cycle d
  • NSId= number of patients with no previous strokes in cycle d
  • SCb= cost of stroke treatment
  • Tf= probability of transfusion of type f
  • TCfg= cost of transfusion, type f (simple, exchange, combined), depending on whether old or new stroke (g)
  • Ghf= probability of complication h when on transfusion type f
  • GCh= cost of complication h
  • SSid = cost of TCD scan in cycle d, depending on previous TCD result (i).

Strokes avoided

Strokes avoided (SA) = nCC − nCI

where:

  • nCC = number of strokes in non-intervention [nCC = (∑PCabcd × Sabce)]
  • nCI = number of strokes in intervention [nCI = (∑PIabcd × Sabce)]

where:

  • PCabcd= number of patients in the age group a and state (mild/moderate/bad/dead) b who have had c strokes in cycle d (PIabcd = patients in intervention group)
  • Sabce= probability of strokes for patients in the age group a and state (mild/moderate/bad/dead) b who have had c strokes, post-stroke state e.

Cost per stroke avoided

Cost per stroke avoided (CPSA) = SAd/iCd

where:

  • SAd= the difference in the number of strokes avoided in the non-intervention scenario compared with the intervention scenario in period d
  • iCd = the difference in cost in the intervention scenario compared with the non-intervention scenario in period d.

Incremental quality-adjusted life-year

Incremental quality-adjusted life-year (iQALY) = QALYlcQALYli

where:

QALYlc=QALY loss(non-intervention)=[SPCbd×(sQALYb+Tf×tQALYf+Gfh×gQALYh)+NSCd×(Tf×tQALYf+Gfh×gQALYh)]
QALYli=QALY loss(intervention)=[SPIbd×(sQALYb+Tf×tQALYf+Gfh×gQALYh)+NSId×(Tf×tQALYf+Gfh×gQALYh)]

where:

  • SPIbd = number of patients in the intervention arm who have had at least one stroke in state b in cycle d
  • SPCbd = number of patients in the non-intervention arm who have had at least one stroke in state b in cycle d
  • NSId = number of patients with no previous strokes in cycle d in the intervention arm
  • NSCd = number of patients with no previous strokes in cycle d in the non-intervention arm
  • sQALYb = QALY loss from stroke treatment, state b
  • Tf = probability of transfusion of type f
  • tQALYf = QALY loss from transfusion, type f (simple, exchange, combined)
  • Ghf = probability of complication h when on transfusion type f
  • gQALYh = QALY loss for complication h.

Incremental cost-effectiveness ratio

ICER = iQALYd/iCostd

where:

  • iQALYd= the difference in QALY loss in the intervention scenario compared with the non-intervention scenario in period d
  • iCostd = the difference in cost in the intervention scenario compared with the non-intervention scenario in period d.
© 2012, Crown Copyright.

Included under terms of UK Non-commercial Government License.

Bookshelf ID: NBK115672
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