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Research Article

Application of an interrupted time series analysis (ITS) to evaluate the effect of universal dialysis policy from 2006 to 2016 in a province of northeastern Thailand

[version 1; peer review: 1 approved with reservations]
PUBLISHED 21 Apr 2023
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Abstract

Background: An interrupted time series (ITS) analysis is a powerful tool for policy evaluation. In Thailand, chronic kidney disease (CKD) is a public health problem that requires a long recovery time and has a high treatment cost. The universal coverage policy for renal replacement therapy (universal dialysis policy), is used to treat this disease but policy evaluation using ITS analysis has rarely been conducted. This study applied ITS analysis to test the effect of such a policy between 2006 and 2016.
Methods: Data were retrieved from the electronic database of the health data center in Roi Et Province for the period between January 1, 2006 and December 31, 2016. 15,681 CKD stage 5 patients were included. The intervention under assessment was the universal health coverage system, which has been implemented since 2008.
Results: Results showed that before implementation of the universal dialysis policy, the overall trend of access to renal replacement therapy (RRT) slightly increased (0.74; 95% confidence interval (CI): 0.58, 0.90). After implementation of the policy, access sharply increased (6.10; 95%CI: 3.67, 8.54), while the linear trend after policy implementation also slightly increased (0.29; 95%CI: 0.05, 0.14). The stratified analysis showed the same linear directional trend before and immediately after implementing the universal dialysis policy.
Conclusions: Implementation of the universal dialysis policy positively impacted the rate of renal replacement therapy in CKD stage 5 patients, while access to health care services also increased.

Keywords

Chronic kidney disease, Universal health coverage, Interrupted time series

Introduction

Chronic kidney disease (CKD) is a major global public health problem. In high-income countries, the prevalence of CKD stages 1-5 in individuals aged ≥20 years is 8.6% in men and 9.6% in women, and in low- and middle-income countries it is 10.6% and 12.5% in men and women respectively.1 In Asia, the prevalence of CKD stages 3-5 is 11.2%.2 CKD has been linked to morbidity and mortality, for example with cardiovascular disease and anemia.3,4 For CKD stage 3-5 patients, renal replacement therapy is considered to be a clinical practice that can consist of the modalities of hemodialysis, peritoneal dialysis, and kidney transplant. In Thailand from 2007 to 2011, the rate of hemodialysis decreased from 79.2% to 54.3%; the rate of peritoneal dialysis increased from 12.2% to 42.9%; while the rate of kidney transplantation decreased from 8.6% to 2.8%.5 Thailand implemented the universal dialysis policy for helping CKD patients to achieve health care treatment in 2008. Since then, there have been several studies related to CKD in Thailand, for example, an epidemiology study of CKD,5 and analyses looking at the prevalence or trend of glomerular filtration rate (GFR) measurement,6 chronic kidney disease prevention and reduction,6 survival rates and related factors for peritoneal dialysis (PD),710 and national peritoneal dialysis.11 However, there has rarely found a study that investigated the effect of the universal treatment policy on the rate of access to health care.

The study design that we used to evaluate the public health policy/intervention in Thailand was an interrupted time series (ITS).12 Several studies have used an ITS to evaluate policies for non-communicable diseases. Few reviews of ITS analysis have been found in regard to policy evaluation concerning CKD.1315 Therefore, the aim of this study was to use an ITS analysis to compare the rate of renal replacement therapy in a province of Northern Thailand before and after the universal coverage of renal replacement therapy was implemented in January, 2008.

Methods

Data sources

A secondary data analysis was used in this study. As a first step we retrieved the data for the period between January 1, 2006 and December 31, 2016 from the Health Data Center (HDC) in Roi Et Province. HDC is a health database system that stores monthly health data since 2007 from all health care services belonging to the Ministry of Public Health, Thailand. The health data comprised demographic data, household data, community (village, activity), health facilities in the community, disability details, provider, service, outpatient department (diagnostic date, procedure, drug and laboratory), inpatient department (admission date, diagnostic date, procedure, drug and laboratory) and the prevalence of communicable diseases. The data does not contain identifying information and cannot be linked to individuals. We selected participants with an estimated GFR (eGFR) of less than 15 ml/min/1.73m2 (CKD stage 5), aged ≥18 years and with universal health coverage were included in our study.

Ethical considerations and consent

The Khon Kaen University Ethics Committee for Human Research approved this study (permit no.: HE642084).

Study variables

The rate of access to renal replacement therapy (RRT) services was calculated by the number of participants accessing treatment for RRT (peritoneal dialysis, hemodialysis) among all dialysis modalities. This data does not include kidney transplant patients. We aggregated the data for each month during the study period. Therefore, the data were created for120 monthly study points between January 1, 2006 and December 31, 2016.

We also collected information including gender (male, female), age (18 to 44 years, 45 to 60 years, > 60 years), and the primary cause of renal failure (hypertension, diabetes, heart disease).

Data analysis

In the ITS analysis, segmented regression was used to test the effect of implementation before, and immediately after the intervention. The strength of the model distinguished the effect of the intervention from secular change. Time series data often have many issues that may affect to the robustness of the analysis such as seasonality, time-varying confounders, use of control, and for other more complex ITS designs, over-dispersion and autocorrelation.12 Seasonality refers to some events occurring more frequently than others, which may affect to the results. Time-varying confounders may occur because of the longitudinal data and age variation across time. Finally, autocorrelation is the correlation between the values of the same variables across different observations (period of the study).16

The dataset for the segmented regression analysis comprised the rate for the event and the time point when the intervention was implemented. An interrupted time series analysis measures trends as slope changes before and after implementation of the intervention, and also the effect seen when the intervention is implemented (the instant effect). Our analysis constructed a series of quarterly rates of access to treatment for renal replacement therapy for CKD stage 5 patients from January 2006 to December 2016. The 24-month pre-intervention period was from January 2006 to December 2007, while the 96-month post-intervention period took place from January 2008 to December 2016. We aggregated the data with 3-month interval. Therefore, there have an 8-time points in the pre-intervention period and 32-time point in post-intervention.

The equation for the ITS analysis17,18 was as follows:

Y=β0+β1×time before interventionx1+β2×interventionx2+β3×time after intervention+et
where Y is the rate of access to renal replacement therapy treatment, β0 is a constant term, and β1 is the coefficient of the time before intervention. Regarding the trend of access to the clinic before implementing the policy, β2 is the coefficient of the intervention immediately (level change), and β3 is the coefficient of time after intervention that refers to the effects of the intervention over time (a different slope before and after intervention). For autocorrelation, we used robustness to fit the model. Stata software, version 12.0, was used to perform all the analyses.

Results

Table 1 shows the characteristics of participants. We included 15,681 patients in the study, which was a total of 1,844 patients before policy (BP) implementation, and 13,837 patients after policy (AP) implementation. 11.76% of the participants were BP and 88.24% of the participants were AP. Most were aged over 60 years and had hypertension conditions, both BP and AP. We also described the rate of treatment for peritoneal dialysis (PD) and hemodialysis that was shown in Table 2.

Table 1. Description of chronic kidney disease (CKD) stage-5 patients, before and after policy implementation.

VariablesTotalBefore policy%After policy%
All15,6811,84411.7613,83788.24
Sex
 Male7,71180810.486,90389.52
 Female7,9701,03613.006,93487.00
Age
 18-441,70424914.611,45585.39
 45-603,90347912.273,42487.73
 >6010,0741,11611.088,95888.92
Primary cause of renal failure
 Hypertension10,0281,03010.278,99889.73
 Diabetes6,2245849.385,64090.62
 Heart Disease3,16038612.222,77487.78
Renal replacement therapy
 Yes2,332472.022,28597.98
  Peritoneal dialysis: PD258--258100.00
  Hemodialysis: HD2,074472.272,02797.73
 No13,3491,79713.4611,55286.54

Table 2. The rate of patients who have had renal replacement therapy (RRT) by sex, age, and primary cause.

VariablesTotalBefore policy%After policy%
Sex
 Male1,048222.10102697.90
 Female1,026252.441,00197.56
Age
 18-44337164.7532195.25
 45-60818151.8380398.17
 >60919161.7490398.26
Primary cause of renal failure
 Hypertension1,864392.091,82597.91
 Diabetes1,337201.501,31798.50
 Heart disease61381.3160598.69

Table 3 shows that the overall trend of access to RRT increased before policy implementation by 0.74 (95%CI: 0.58, 0.90), while after policy implementation the trend sharply increased by 6.10 (95%CI: 3.67, 8.54). The linear trend after policy implementation slightly increased by 0.29 (95%CI: 0.17, 0.41). The overall trend is shown in Figure 1. For those aged 60 or over, the trend slightly increased before policy implementation, while immediately after policy implementation the trend sharply increased by 5.26 (95%CI: 3.50, 7.01). For those whose primary cause of renal failure was diabetes, hypertension, and heart disease, the trend after policy implementation sharply increased by 9.11 (95%CI: 5.25,12.96), 7.65 (95%CI: 2.22, 13.07), and 11.83 (95%CI: 5.44, 18.22) respectively.

Table 3. Results from the interrupted time series (ITS) on the rate of access to renal replacement therapy before and after policy implementation.

Trend before policyChange in level after policyLinear trend after policy
β (95% CI)P valueβ (95% CI)P valueβ (95% CI)P value
All0.74 (0.58, 0.90)<0.0016.10 (3.67, 8.54)<0.0010.29 (0.17, 0.41)<0.001
Sex
 Male0.79 (0.52, 1.07)<0.0015.69 (2.34, 9.03)0.0010.29 (0.14, 0.44)0.0004
 Female0.70 (0.55,0.84)<0.0016.72 (4.46, 8.98)<0.0010.27 (0.15, 0.38)<0.001
Age
 18-442.31 (1.07, 3.56)0.0012.93 (-6.13, 12.00)0.5170.20 (0.047, 0.35)0.0119
 45-601.15 (0.76, 1.55)<0.0019.05 (5.08, 13.02)<0.0010.52 (0.36, 0.69)<0.001
 >600.40 (0.32, 0.49)<0.0015.26 (3.50, 7.01)<0.0010.18 (0.10, 0.26)0.0001
Primary cause of renal failure
 Diabetes
  Yes1.50 (1.21, 1.79)<0.0019.11 (5.25, 12.96)<0.0010.37 (0.19, 0.56)0.0002
  No0.50 (0.08, 0.92)0.022.93 (-0.59, 6.47)0.1010.15 (0.06, 0.23)0.0012
 Hypertension
  Yes1.28 (0.73, 1.85)<0.0017.65 (2.22, 13.07)0.0070.32 (0.07, 0.18)0.0001
  No0.09 (-0.29, 0.46)0.6431.95 (-0.71, 4.60)0.1460.03 (-0.04, 0.09)0.387
 Heart disease
  Yes0.64 (0.04, 1.24)0.03611.83 (5.44, 18.22)0.0010.44 (0.21, 0.67)0.0004
  No0.82 (0.56, 1.09)<0.0013.38 (0.41, 6.35)0.0260.28 (0.15, 0.40)0.0001
f93b5560-7b2e-42b7-ae4f-f1d858434858_figure1.gif

Figure 1. The rate of overall renal replacement therapy (RRT) from the interrupted time series (ITS).

Discussion

Results showed that before implementing the universal dialysis policy, the trend of access to RRT slightly increased, while immediately after implementing the universal dialysis policy the trend sharply increased.

Before policy implementation in 2008, evidence showed that the rate of access to RRT slightly increased, possible as a result of the universal coverage policy not covering RRT. This meant that patients were responsible for medication payments (approximately 1,500 Thai baht per visit),19 which affected their decision to undergo the therapy. The long-term treatment of RRT and high payments made low-income patients unable to access a clinic and receive appropriate treatment.

Because of his, the National Health Security Office (NHSO) developed a kidney replacement therapy service system for patients with end-stage chronic renal failure in 2008. This policy was called ‘CAPD first’ and covered renal replacement therapy, kidney transplantation (KT), peritoneal dialysis (PD) and hemodialysis (HD). It provides peritoneal dialysis as the first choice and hemodialysis only for those who are unable to undergo peritoneal dialysis or who have a medical indication prohibiting PD. In the case of an old hemodialysis patient who does not voluntarily undergo peritoneal dialysis, the patient will have to pay 1/3 of the service fee (patients pay no more than 500 baht and NHSO pays 1,000 baht per time).19 This new system resulted in a significantly higher rate of RRT patients with stage 5 renal failure. There are still many patients with renal failure who have not decided to enter the treatment system. Our evidence confirmed that after implementing this policy in 2008, the rate of access to RRT sharply increased and it helped patients to receive treatment because they did not have to bear the expenses themselves but gained benefits allocated by the state.

Prevalence of renal replacement therapy in Thailand

The total yearly incidence of RRT increased by an average of 14.8% after the implementation of the universal coverage policy for renal replacement therapy (known first as CAPD) and the yearly incidence of all RRT modalities increased by an average of 34.8% in 2007 to 2009.20 A report by Thai Renal Replacement Therapy (TRT) stated that the number of end-stage renal failure patients receiving renal replacement services increased from 68.34 per million in 2006 to over 181 per million in 2009 (or more than 11,500 new patients per year). The number of people receiving renal replacement services increased significantly from 419 per million to over 639 per million (or more than 40,000 in 2009).21 Our analysis results also showed that the linear trend of RRT after implementing the continuous policy slightly increased. Despite the expected increased volume of patients, the year-by-year growth rate of patients in all RRT modalities seemed to diminish over time.22 due to the CAPD first policy. HD is performed only for those who are unable to undergo peritoneal dialysis or who have a medical indication prohibiting PD. Therefore, HD dialysis will be covered.23 Some patients who meet the criteria for HD decide not to enroll for CAPD due to lack of readiness for the treatment required, such as inappropriate accommodation, lack of caregivers, being unsure of self-cleaning processes at home and fear of infection after the procedure.24

A slight increase in access to RRT services was in line with the assessment of access to services and the provision of renal replacement services under the health insurance system in Thailand. The expected number of patients who accessed the services was more than 35,000 in 2011, but there are only 19,000 cumulative cases under the UHC scheme. At the end of the fiscal year 2012, the number of patients was estimated at more than 48,000 patients, but the cumulative number of cases was only about 23,000.25 In terms of service provision, some hospitals are unable to participate in the universal health insurance program or are unable to provide services. Due to the availability of human resources and location, a health care service might require patients to go to other hospitals that can provide services but are far from their homes, which made it inconvenient and costly for traveling. This might be a consideration when making the decision to select a treatment.

Strengths and limitations

Our study had some limitations. Firstly, data retrieved from other hospitals might have different methods that could have impacted data quality. Secondly, only two hospitals currently incorporate this scheme and one is a private hospital, so some data were incomplete. Finally, our results might not be generalizable to Thailand as a whole because we analyzed data from only one province. However, the strength of our study is an analysis using the interrupted time series model that accurately interpreted the results.

Conclusions

Our results revealed that after the universal coverage of renal replacement therapy policy implementation, the rate of treatment for RRT slightly increased. Extensive data collection from other health centers would be useful for further research. After the policy implementation, the trends in access to RRT slightly increased. This might be because patients were uncertain about using CAPD at their houses. To further increase the rate of RRT, policy makers should consider this point.

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Pukdeesamai P, Sarakarn P and Anutrakulchai S. Application of an interrupted time series analysis (ITS) to evaluate the effect of universal dialysis policy from 2006 to 2016 in a province of northeastern Thailand [version 1; peer review: 1 approved with reservations]. F1000Research 2023, 12:434 (https://doi.org/10.12688/f1000research.128094.1)
NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article.
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ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested
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Not approvedFundamental flaws in the paper seriously undermine the findings and conclusions
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Reviewer Report 04 Oct 2024
Yao Wu, Monash University, Clayton, Victoria, Australia 
Approved with Reservations
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This study assesses the impact of a universal dialysis policy from 2006 to 2016 in a province of north-eastern Thailand using an interrupted time series (ITS) analysis. The authors have made a good start, but the study requires further refinement, ... Continue reading
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Wu Y. Reviewer Report For: Application of an interrupted time series analysis (ITS) to evaluate the effect of universal dialysis policy from 2006 to 2016 in a province of northeastern Thailand [version 1; peer review: 1 approved with reservations]. F1000Research 2023, 12:434 (https://doi.org/10.5256/f1000research.140653.r322049)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.

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Alongside their report, reviewers assign a status to the article:
Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions
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