To the best of our knowledge, this is the first study to demonstrate the effect of full subsidies and nudge theory on hepatitis screening rates in Japanese worksites. These findings suggest that (i) making screenings free of charge led to the greatest increase in screening uptake, potentially saving many lives and (ii) modifying client reminders using nudge theory could produce a substantial increase in screening uptake at lower costs, making it a viable option in limited-resource settings.
Findings
Fully subsidized hepatitis virus screening had the highest screening rate of 86.3%, compared to 37.1% for the nudge-based reminder only and 21.2% for the control reminder. The effect of the intervention, expressed as the risk ratio to the control reminder, was 4.08 (95% CI 3.44–4.83) for full subsidy and 1.75 (95% CI 1.45–2.12) for the nudge-based reminder only. In addition, the parameters were significantly positive for both group A and group B, even after adjusting for heterogeneity due to clusters. Previous studies on cancer screening also showed a rise in screening uptake when fully subsidized [
18‐
20]. However, in our study, the cost of screening was only JPY 612 in the nudge-based client reminder only group, yet screening was 49.2% lower. This suggests that requiring a co-payment, albeit small, could discourage many people from undergoing screening. Therefore, if feasible, removing co-payments could promote screening in hard-to-reach populations.
Our study also suggests that applying nudge theory to client reminders increased the hepatitis virus screening rates in these worksites. In particular, our results suggest that providing too much information might reduce the readability of the message, while using nudge-based reminders may increase screening rates in this context. Likewise, a previous study demonstrated that nudge-based client reminders increased colorectal cancer screening rates [
14]. To design the nudge-based reminders in this study, we referred to the EAST framework proposed by the UK BIT in their executive report [
17], which consists of four principles: (i) “Easy,” (ii) “Attractive,” (iii) “Social,” and (iv) “Timely”. This study followed the principles of “Easy” and “Attractive”. UK BIT recommends, as part of the “Easy” principle, to simplify messages and make them easy to understand. In line with this recommendation, we reduced the number of words on the client reminder. The “Attractive” principle emphasized the importance of drawing attention to important aspects of a message. To this end, the discounted cost of the screening was made salient by striking out the original cost of screening (JPY 2040) and using capital letters for the new cost (JPY 612).
Although making the hepatitis virus screening free produced the highest hepatitis virus screening rates, this led to additional costs. Thus, we performed an incremental cost-effectiveness ratio (ICER) to evaluate the cost-effectiveness of these interventions. The ICER was JPY 1168.7 and JPY 172.5 for the full subsidies and nudge-based reminder only, respectively. Therefore, simply applying nudge theory could significantly increase hepatitis virus screening at lower costs per person, which is critical in low resource settings where offering free screening is not feasible [
21,
22]. This finding has implications even at the policy level. In 2011, the Japanese government decided to offer a free coupon for hepatitis virus screening, spending as much as JPY 3.3 billion yen. However, screening increased only by 446,000 people compared to previous year [
23,
24]. If the nudge-based reminder were used, it could have cost substantially less and with better cost-effectiveness.
These results also have implications that could affect social implementation. In our study, the ICER of group A is smaller than that of group B. However, it is possible for this relationship to be reversed if the design costs (more generally speaking, fixed costs) are very large. In fact, for the current sample size, number of screening takers, unit cost of full subsidy, and printing costs, that reversal will happen when the design cost exceeds JPY 914,789. On the other hand, a larger design cost means that the absolute value of the ICER will increase in both groups A and B, which means that the financial burden on the insurer will be greater than in the present case. In light of this, the intervention should be implemented with as little design or fixed costs as possible, and, in such cases, the nudge-based reminder only will most likely be more cost-effective.
Even though there were approximately 17 million JHIA subscribers in 2018, only 2 million people received hepatitis testing by the end of 2018 [
25]. Therefore, we estimated the impact of scaling up the nudge-based client reminder intervention to all 17 million members of JHIA subscribers if screening rates for both HBV and HCV increased by 16% as shown in our study:
1.
The total cost to send nudge-based client reminders will be 341 million yen (20 yen per person for printing and 20,000 yen for designing).
2.
Approximately 16,408 HBV carriers and 8204 HCV carriers could be identified (infection rates among the general population for HBV and HCV are estimated at 0.6% and 0.3%, respectively, according to literature) [
26,
27].
3.
If all the HCV carriers complete their treatment, an estimated 5824 cases of liver cirrhosis could be prevented (approximately 71% of HCV carriers develop liver cirrhosis [
28]).
4.
About 1514 liver cancer cases can be prevented (26% of HCV liver cirrhosis cases typically develop into liver cancer [
29]).
Limitations
This research has several limitations. First, this study was conducted on employees who applied for and attended general health checkups. Because of the nature of these participants, hepatitis virus screening behavior might differ from that of the general population or from employees who did not sign up for the general health checkups. Second, the positive rates for HCV (0.2%, 0%, and 1.3% for the control group, group A, and group B, respectively) and the HBV (0% for all three groups) were different from our earlier expectations of 0.6% for HBV, and 0.3% for HCV based on previous studies [
26]. However, the limited reliability of our measured positive rates due to a small sample size makes it difficult to draw valid comparisons. Third, the demographic data of the sample population is limited to sex and age because the transportation company is not permitted under the Industrial Safety and Health Act to obtain the results of optional tests since companies could identify employees who tested positive and put them at a disadvantage [
16]. Hence, further studies are needed to address these limitations. Fourth, the analysis only included 13 clusters. However, after adjusting for heterogeneity of each cluster, our study found significant intervention effects. Nevertheless, increasing the number of clusters might allow us for more precise estimations of effects.