From Spreadsheets to Script: Experiences From Converting a Scottish Cardiovascular Disease Policy Model into R

Given the advantages in transparency, reproducibility, adaptability and computational efficiency in R, there is a growing interest in converting existing spreadsheet-based models into an R script for model re-use and upskilling training among health economic modellers. The objective of this exercise was to convert the Scottish Cardiovascular Disease (CVD) Policy Model from Excel to R and discuss the lessons learnt throughout this process. The CVD model is a competing risk state transition cohort model. Four health economists, with varied experience of R, attempted to replicate an identical model structure in R based on the model in Excel and reproduce the intermediate and final results. Replications varied in their use of specialist health economics packages in addition to standard data management packages. Two versions of the CVD model were created in R along with a Shiny app. Version 1 was developed without health economics specialist packages and produced identical results to the Excel version. Version 2 used the heemod package and did not achieve the same results, possibly due to the non-standard elements of the model and limited time to adapt the functions. The R model requires less than half the computational time than the Excel model. Conversion of the spreadsheet models to script models is feasible for health economists. A step-by-step guide for the conversion process is provided and modellers' experience is discussed. Coding without specialist packages allows full flexibility, while specialist packages may add convenience if the model structure is suitable. Whichever approach is taken, transparency and replicability remain the key criteria in model programming. Model conversions must maintain standards in these areas regardless of the choice of software.

Real-World Estimates of Adrenal Insufficiency-Related Adverse Events in Children With Congenital Adrenal Hyperplasia

BACKGROUND

Although congenital adrenal hyperplasia (CAH) is known to be associated with adrenal crises (AC), its association with patient- or clinician-reported sick day episodes (SDE) is less clear.

METHODS

Data on children with classic 21-hydroxylase deficiency CAH from 34 centers in 18 countries, of which 7 were Low or Middle Income Countries (LMIC) and 11 were High Income (HIC), were collected from the International CAH Registry and analyzed to examine the clinical factors associated with SDE and AC.

RESULTS

A total of 518 children-with a median of 11 children (range 1, 53) per center-had 5388 visits evaluated over a total of 2300 patient-years. The median number of AC and SDE per patient-year per center was 0 (0, 3) and 0.4 (0.0, 13.3), respectively. Of the 1544 SDE, an AC was reported in 62 (4%), with no fatalities. Infectious illness was the most frequent precipitating event, reported in 1105 (72%) and 29 (47%) of SDE and AC, respectively. On comparing cases from LMIC and HIC, the median SDE per patient-year was 0.75 (0, 13.3) vs 0.11 (0, 12.0) (P < 0.001), respectively, and the median AC per patient-year was 0 (0, 2.2) vs 0 (0, 3.0) (P = 0.43), respectively.

CONCLUSIONS

The real-world data that are collected within the I-CAH Registry show wide variability in the reported occurrence of adrenal insufficiency-related adverse events. As these data become increasingly used as a clinical benchmark in CAH care, there is a need for further research to improve and standardize the definition of SDE.

MON-170 Real World Estimates of Adrenal Insufficiency Related Adverse Events in Children with Congenital Adrenal Hyperplasia: On Behalf of the I-CAH Consortium

Background Although congenital adrenal hyperplasia (CAH) is a rare condition, it is the commonest cause of early-onset primary adrenal insufficiency and places the patient at a life-long risk of sick day episodes (SDE) and adrenal crises (AC). Objective To investigate the epidemiology of SDE and AC in an international cohort of patients <18 yrs old with 21-OH deficiency CAH. Methods Multi-level logistic model analysis of data in the International CAH (I-CAH) registry (www.i-cah.org) to examine the clinical associations of SDE, AC, stress-dose days and hospitalisations. Results 518 patients (F, 53%) from 34 centres in 18 countries with a median number of cases per centre of 12 (IQR 1-26), had a total of 5388 reported visits with a median duration of follow-up per patient of 3.1 yrs (IQR 2.5-5.8). Of the 518 patients, 334 (64%) had ≥1 SDE; the median number of SDE per patient year per centre was 1.0 (IQR 0.4-2.2) and the median duration of SDE was 3.0 days (IQR 2.0-5.0). Children between 1-4 yrs and adolescents (15-18 yrs) had a greater risk of SDE [OR 2.02 (95%CI:1.60,2.56) and OR 1.64 (95%CI:1.34,2.02), respectively] and stress-dosing [OR 2.03 (95%CI:1.56,2.60) and OR 1.63 (95%CI:1.32,2.02), respectively] compared to children <1 yr old. Males were more likely to have a SDE [OR 1.40 (95%CI:1.13,1.73) and stress-dosing [OR 1.40 (95%CI:1.12,1.76) than females. An AC was reported in 4% of SDE (62/1544) with 92% of visits associated with hospital admission. Infectious illness was the most frequent associated event and was reported in 72% (1105/1544) of SDE and 47% (29/62) of AC. Males had a higher risk of AC compared to females [OR 1.03 (95%CI:1.03,1.03). Children with salt-wasting CAH were more likely to be hospitalised during a SDE, compared with those with simple-virilising CAH [OR 2.08 (95%CI:0.99,7.91)]. Children receiving glucocorticoid (GC) doses within the hydrocortisone (HC) equivalent dose (ED) of 10-15mg/m²/d were more likely to have SDE [OR 1.66 (95%CI:1.31,2.10), stress-dosing [OR 1.85 (95%CI:1.44,2.37) and AC [OR 1.08 (95%CI:1.08,1.08), p<0.001] than children on HC ED >15mg/m²/day. Similarly, children on HC ED <10mg/m²/d were more likely to have SDE [OR 2.20 (95%CI:1.66,2.90)], stress-dosing [OR 2.37 (95%CI:1.77,3.19)] and AC [OR 8.34 (95%CI:8.33,8.35), p<0.001] than those on higher doses. Children on FC doses between 50-200mcg/day and lower than 50 mcg were less likely to have AC [OR 4.54 (95%CI:4.54,4.55) and OR 8.58 (95%CI:8.57,8.59), respectively] than those on higher doses (>200mcg/day). Oral GC were increased in 74% (1147/1544) of SDE whilst HC injection was administered in 11% (176/1544) of SDE. Conclusions The real-world data within the I-CAH registry are a valuable resource for identifying factors that place a child with CAH at a higher risk of adverse events and can be used in prediction models for calculating individual risk.

Impact of legislation to reduce the drink-drive limit on road traffic accidents and alcohol consumption in Scotland: a natural experiment study

Background

It is widely recognised that drink driving is a leading cause of road traffic accidents (RTAs). There is evidence that changing the drink-drive limit from a blood alcohol concentration of 0.08 to 0.05 g/dl is effective in reducing RTAs. Scotland changed the blood alcohol concentration limit to 0.05 g/dl on 5 December 2014.

Aims

To assess whether or not the numbers and rates of RTAs and per capita alcohol consumption in Scotland were reduced because of the 2014 drink-drive legislation. To assess whether or not the 2014 change in legislation provided good value for money.

Design

A natural experimental, quantitative study. The control group was England and Wales, that is, the other countries in Great Britain, where the drink-drive legislation remained unchanged.

Setting

Great Britain.

Participants

The entire population of Scotland, England and Wales for the period of January 2013–December 2016.

Intervention

The change to drink-drive legislation in Scotland.

Outcome measures

The counts and rates of RTAs; and per capita alcohol consumption.

Methods

For the numbers and rates of RTAs (both traffic flow and population denominators were used), and separately for the intervention and control trial groups, negative binomial regression models were fitted to panel data sets to test for a change in outcome level after the new 2014 legislation was in place. To obtain a ‘difference-in-differences’ (DiD)-type measure of effect, an interaction term between the intervention group indicator and the binary covariate for indicating pre and post change in legislation (‘pseudo’-change for the control group) was assessed. For off- and on-trade per capita alcohol sales, and separately for the intervention and control trial group, seasonal autoregressive integrated moving average error models were fitted to the relevant time series.

Results

The change to drink-drive legislation was associated with a 2% relative decrease in RTAs in Scotland [relative risk (RR) 0.98, 95% CI 0.91 to 1.04; p = 0.53]. However, the pseudo-change in legislation was associated with a 5% decrease in RTAs in England and Wales (RR 0.95, 95% CI 0.90 to 1.00; p = 0.05). For RTA rates, with traffic flow as the denominator, the DiD-type estimate indicated a 7% increase in rates for Scotland relative to England and Wales (unadjusted RR 1.07, 95% CI 0.98 to 1.17; p = 0.1). The change to drink-drive legislation was associated with a 0.3% relative decrease in per capita off-trade sales (–0.3%, 95% CI –1.7% to 1.1%; p = 0.71) and a 0.7% decrease in per capita on-trade sales (–0.7%, 95% CI –0.8% to –0.5%; p < 0.001).

Conclusion

The change to drink-drive legislation in Scotland in December 2014 did not have the expected effect of reducing RTAs in the country, and nor did it change alcohol drinking levels in Scotland. This main finding for RTAs was unexpected and the research has shown that a lack of enforcement is the most likely reason for legislation failure.

Future work

Investigations into how the public interpret and act on changes in drink-drive legislation would be welcome, as would research into whether or not previous change in drink-drive legislation effects on RTAs in other jurisdictions are associated with the level of enforcement that took place.

Trial registration

Current Controlled Trials ISRCTN38602189.

Funding

This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 7, No. 12. See the NIHR Journals Library website for further project information.

An evaluation of the effects of lowering blood alcohol concentration limits for drivers on the rates of road traffic accidents and alcohol consumption: a natural experiment

BACKGROUND

Drink driving is an important risk factor for road traffic accidents (RTAs), which cause high levels of morbidity and mortality globally. Lowering the permitted blood alcohol concentration (BAC) for drivers is a common public health intervention that is enacted in countries and jurisdictions across the world. In Scotland, on Dec 5, 2014, the BAC limit for drivers was reduced from 0·08 g/dL to 0·05 g/dL. We therefore aimed to evaluate the effects of this change on RTAs and alcohol consumption.

METHODS

In this natural experiment, we used an observational, comparative interrupted time-series design by use of data on RTAs and alcohol consumption in Scotland (the interventional group) and England and Wales (the control group). We obtained weekly counts of RTAs from police accident records and we estimated weekly off-trade (eg, in supermarkets and convenience stores) and 4-weekly on-trade (eg, in bars and restaurants) alcohol consumption from market research data. We also used data from automated traffic counters as denominators to calculate RTA rates. We estimated the effect of the intervention on RTAs by use of negative binomial panel regression and on alcohol consumption outcomes by use of seasonal autoregressive integrated moving average models. Our primary outcome was weekly rates of RTAs in Scotland, England, and Wales. This study is registered with ISRCTN, number ISRCTN38602189.

FINDINGS

We assessed the weekly rate of RTAs and alcohol consumption between Jan 1, 2013, and Dec 31, 2016, before and after the BAC limit came into effect on Dec 5, 2014. After the reduction in BAC limits for drivers in Scotland, we found no significant change in weekly RTA rates after adjustment for seasonality and underlying temporal trend (rate ratio 1·01, 95% CI 0·94-1·08; p=0.77) or after adjustment for seasonality, the underlying temporal trend, and the driver characteristics of age, sex, and socioeconomic deprivation (1·00, 0·96-1·06; p=0·73). Relative to RTAs in England and Wales, where the reduction in BAC limit for drivers did not occur, we found a 7% increase in weekly RTA rates in Scotland after this reduction in BAC limit for drivers (1·07, 1·02-1·13; p=0·007 in the fully-adjusted model). Similar findings were observed for serious or fatal RTAs and single-vehicle night-time RTAs. The change in legislation in Scotland was associated with no change in alcohol consumption, measured by per-capita off-trade sales (-0·3%, -1·7 to 1·1; p=0·71), but a 0·7% decrease in alcohol consumption measured by per-capita on-trade sales (-0·7%, -0·8 to -0·5; p<0·0001).

INTERPRETATION

Lowering the driving BAC limit to 0·05 g/dL from 0·08 g/dL in Scotland was not associated with a reduction in RTAs, but this change was associated with a small reduction in per-capita alcohol consumption from on-trade alcohol sales. One plausible explanation is that the legislative change was not suitably enforced-for example with random breath testing measures. Our findings suggest that changing the legal BAC limit for drivers in isolation does not improve RTA outcomes. These findings have significant policy implications internationally as several countries and jurisdictions consider a similar reduction in the BAC limit for drivers.

FUNDING

National Institute for Health Research Public Health Research Programme.

The impact of TV mass media campaigns on calls to a National Quitline and the use of prescribed nicotine replacement therapy: a structural vector autoregression analysis

AIMS

To estimate (1) the immediate impact; (2) the cumulative impact; and (3) the duration of impact of Scottish tobacco control TV mass media campaigns (MMCs) on smoking cessation activity, as measured by calls to Smokeline and the volume of prescribed nicotine replacement therapy (NRT).

DESIGN

Multivariate time-series analysis using secondary data on population level measures of exposure to TV MMCs broadcast and smoking cessation activity between 2003 and 2012.

SETTING AND PARTICIPANTS

Population of Scotland.

MEASUREMENTS

Adult television viewer ratings (TVRs) as a measure of exposure to Scottish mass media campaigns in the adult population; monthly calls to NHS Smokeline; and the monthly volume of prescribed NRT as measured by gross ingredient costs (GIC).

FINDINGS

Tobacco control TVRs were associated with an increase in calls to Smokeline but not an increase in the volume of prescribed NRT. A 1 standard deviation (SD) increase of 194 tobacco control TVRs led to an immediate and significant increase of 385.9 [95% confidence interval (CI) = 171.0, 600.7] calls to Smokeline (unadjusted model) within 1 month. When adjusted for seasonality the impact was reduced, but the increase in calls remained significant (226.3 calls, 95% CI = 37.3, 415.3). The cumulative impact on Smokeline calls remained significant for 6 months after broadcast in the unadjusted model and 18 months in the adjusted model. However, an increase in tobacco control TVRs of 194 failed to have a significant impact on the GIC of prescribed NRT in either the unadjusted (£1361.4, 95% CI = -£9138.0, £11860.9) or adjusted (£6297.1, 95% CI = -£2587.8, £15182.1) models.

CONCLUSIONS

Tobacco control television mass media campaigns broadcast in Scotland between 2003 and 2012 were effective in triggering calls to Smokeline, but did not increase significantly the use of prescribed nicotine replacement therapy by adult smokers. The impact on calls to Smokeline occurred immediately within 1 month of broadcast and was sustained for at least 6 months.