Parameter | Description | Data sources | Derivation of required probabilities | Point estimate (standard error (SE) | Distribution |
---|---|---|---|---|---|
pSafe | Baseline prevalence of safe storage of medicines | Case control study of risk and protective factors for poison injuries in under 5 year olds (Kendrick et al, paper om press). | Number of households with safe storage of medicines/Total number of households selected as community controls in case control of risk and protective factors in children under 5 years old (Kendrick et al, paper om press). | 1527/2033 = 0.75 | Beta |
pAccept | Probability of accepting the intervention | Saramago, Cooper et al., 2015 [14] | Assumption based on value in Functional smoke alarm model. Assumed the same for all interventions. | 0.90 | Fixed |
pEff | Probability of safe storage of medicines given the intervention | Achana et al., 2015 [9] | (1) Usual care (2) Education (3) Provision of low cost/free low cost/free equipment (4) Education + provision of low cost/free equipment (5) Education + equipment + home safety inspection (6) Education + equipment + fitting (7) Education + equipment + home safety inspection + fitting | 0.87 (95%CrI 0.56, 0.98) 0.90 (95%CrI 0.61, 0.98) 0.93 (95%CrI 0.65, 0.99) 0.94 (95%CrI 0.74, 0.99) 0.90 (95%CrI 0.56, 0.99) 0.90 (95%CrI 0.59, 0.98) 0.93 (95%CrI 0.66, 0.99) | Posterior distribution of absolute intervention effects from network meta-analysis. |
pIngest | Probability of unintentional exposure/ingestion | Orton et al., 2014 [10] Tyrrell et al., 2012 [33] Office for National Statistics, 2013 [34] | Orton et al [10] – incidence of poisonings in the UK for period 2005–2009 is 30.1 (95 % CI 29.1–31.2). Mid-year population estimates of under 5 year olds in the UK in 2012 = 3996400 [34]. Hence number of poisoning cases = (30.1*3996400)/10000 = 12029. The numerator (n = 12029*0.6 = 7217) was derived based on information in [33] suggesting that 1316 (60 %) of the 2193 medically reported poisonings identified in the THIN database were due to ingestion of a medicinal substance. | 7217/3996400 = 0.001806 | Beta |
orIngest | Relative risk of exposure to a medicinal substance comparing children with a poisoning to community controls. | Case control study of risk and protective factors for poison injuries in under 5 year olds (unpublished study) | Community controlled adjusted analysis odds ratio for safe storage versus no safe storage = 1.83 (95 % CI 1.38–2.42) | Log odds ratio (SE) = -0.604 (0.143) | Normal |
pAmb | Probability of using emergency ambulance. | Hospital Episode Statistics, 2012 | Hospital Episode Statistics (2012b): 24.2 % of all cases arrived by emergency transfer (ambulance/helicopter). | 0.242 | Fixed |
pAdmit | Probability of in-patient admission following a medicinal poisoning injury (ICD-10: X40-X44). | Hospital Episode Statistics, 2013 [35] Office for National Statistics, 2013 [34] | Hospital Episode Statistics, 2012–2013) [35]: Number of poisoning cases (X40-X44) admitted in 0–4 years olds (period 2012–2013) in England = 3909. Scaled up by a factor of 1.163 (i.e. 3909*1.163 = 4546 cases for whole of UK) based on mid-2012 population estimates for UK and England [34]. | 4546/7217 = 0.63 | Beta |
pSevere | Probability of severe poisoning injury | Mowry et al., 2013 [36] | NPDS 2012 report [36], Table 13, page 968) 1.91 % of major poisoning cases (across all age groups) resulted in a chronic health condition. Numerator = 0.019* 4546 = 87. | 87/4546 = 0.0191 | Beta |
pFatal | Probability of fatal poisoning injury. | Office for National Statistics, 2012 [37] | UK mortality statistics [37]. 1 fatality from medicinal poisonings in 0–4 years old (assumed fatality occur after a long inpatient stay). | 1/86 = 0.0116 | Beta |
pDead | UK mortality statistics | Office for National Statistics, 2010 [38] | UK mortality statistics [38] | Normal |