Number needed to treat and cost-effectiveness in the prevention of ventilator-associated pneumonia

clinicians continue to redefi ne ventilator-associated pneumonia (VAP), numerous innovations that claim to reduce pulmonary microaspiration and its consequences – that is, novel endotracheal cuff shapes and cuff materials, subglottic drainage, automatic cuff pressure controllers, oral antiseptics , selective digestive decontamination (SDD), and devices to combat biofi lm formation within the lumen of the tracheal tube – are coming to the market [1,2]. Th ere are two questions that clinicians ask when deciding whether to incorporate a new product or intervention into a VAP prevention bundle. Firstly, what are its effi cacy and eff ectiveness? In other words, what is the relative risk reduction (RRR) and therefore the number needed to treat (NNT) to prevent one additional VAP. Secondly, is this new intervention cost-eff ective in my local patients? To answer the fi rst question, one needs data from clinical trials and the knowledge of the baseline VAP rate with the likely RRR of the local case mix. We have calculated (Table 1) the NNT required to prevent one additional VAP for patients who require intubation and mechanical ventilation (MV) for more than 72 hours and an average time of MV of 10 days. Th e NNTs are based on an RRR ranging from 5% to 50% and a control event rate for VAP ranging from 1% to 20%, given a uniform distribution of NNTs across the range of RRRs. For example, with a VAP rate of approximately 8% and an intervention that reduces VAP by 45%, the NNT is 28 – a scenario that is realistic given a recent meta-analysis of one particular intervention [3]. To establish whether the intervention is cost-eff ective, further knowledge of the cost of the intervention and the cost to treat an episode of VAP is required. A recent US study estimated the cost of VAP to be nearly $40,000 (£25,000 or €30,000) [4]. If costs are assumed to be lower in Europe, then a conservative estimate of the cost per episode of VAP would still be around £10,000, which is equivalent to an extra 7 days of intensive care unit (ICU) stay. What should we consider when assessing the cost-eff ectiveness of VAP prevention? We have calculated (Table 2) the additional money (in pounds) that can be spent to prevent an episode of VAP (per 10 days of MV) to achieve cost-neutrality. If we assume a hypothetical VAP cost of £10,000, then with …