Comparing the Sensitivities of Measures of Adherence to Antihypertensive Drugs Using Korean National Health Insurance Claims Data

Figures & data

Figure 1 Descriptive definitions of medication adherence measures including PDCwith≥1, PDCwm, and DPPR.

Notes: The right part describes how three measures are calculated and applied to derive medication adherences as hypothetical scenarios of claim data. Each box covers 10 days and a box with blue color means days’ supply.

Abbreviations: PDCwith≥1, proportion of days covered with one or more medications; PDCwm, duration weighted mean PDC; DPPR, daily polypharmacy possession ratio.

Table 1 Baseline Characteristics of Study Population in the Base-Case Setting

Characteristic		Total
		N(%)
Overall		14,288
Sex	Male	7440 (52.1)
	Female	6848 (47.9)
Age	Mean ± SD	57.42 ±12.86
	20–39	1111 (7.8)
	40–49	3068 (21.5)
	50–59	3897 (27.3)
	60–69	3499 (24.5)
	≥70	2713 (19.0)
Disability	Yes	1219 (8.5)
Antihypertensive therapy	Mono therapy	8696 (60.9)
	Dual therapy	4267 (29.9)
	≥3 classes	1325 (9.3)
Type of health insurance	Regional	4672 (32.7)
	Employment-based	8527 (59.7)
	Medical aid	1089 (7.6)
Number of medical institution visited	1	5380 (37.7)
	2	4477 (31.3)
	≥3	4431 (31.0)
Insurance contributions	High	5504 (38.5)
	Moderate	4749 (33.2)
	Low	4035 (28.2)

Table 2 Diverse Impacts of Measures of Medication Adherence with Varied Options on PDC_with≥1

Decision Node		N	PDCwith≥1		Rate of Adherent Patients (≥ 80%)
			Mean ± SD	Median (Q1–Q3)	N (%)	p-value
Category 1: Definition of data cleaning
1. Elimination claims that are irregular for hypertension medication
a. In-hospital medication initiation	14,311		75.91 ±24.85	85.96 (61.70–95.75)	8367 (58.5)	0.03
b. In-hospital medication initiation or use of injectable agents	14,306		75.92 ±24.84	85.98 (61.72–95.75)	8368 (58.5)
c. Short-term prescribing under 7 days*	14,288		76.70 ±24.59	86.80 (63.05–96.15)	8549 (59.8)
Difference (Max - Min)	23		0.79	0.84	182
2. Elimination of redundant duplicate claims
a. Deduplication*	14,288		76.70 ±24.59	86.80 (63.05–96.15)	8549 (59.8)	0.32
b. Leave as it was	14,276		77.03 ±24.65	87.37 (63.48–96.47)	8624 (60.4)
Difference (Max - Min)	12		0.33	0.57	75
Category 2: Inclusion criteria and observation period
3. Inclusion criteria for a minimum number of prescriptions
a. At least two prescriptions*		14,288	76.70 ±24.59	86.80 (63.05–96.15)	8549 (59.8)	0.84
b. At least four prescriptions		14,014	76.89 ±24.31	86.81 (63.39–96.12)	8402 (60.0)
Difference (Max - Min)		274	0.19	0.01	147
4. Inclusion criteria for pre-index period
a. 180 days		16,397	75.82 ±24.79	85.68 (61.50–95.87)	9506 (58.0)	<0.0001
b. 365 days*		14,288	76.70 ±24.59	86.80 (63.05–96.15)	8549 (59.8)
c. 730 days		12,656	77.26 ±24.46	87.51 (64.13–96.34)	7748 (61.2)
Difference (Max - Min)		3741	1.44	1.83	1758
5. Inclusion criteria for supply for the minimum cumulative number of days
a. 30 days		15,510	74.42 ±27.11	85.74 (59.14–96.05)	8956 (57.7)	<0.0001
b. 90 days*		14,288	76.70 ±24.59	86.80 (63.05–96.15)	8549 (59.8)
c. 180 days		13,194	79.19 ±21.73	87.93 (67.32–96.34)	8237 (62.4)
d. 1 year		11,802	83.12 ±17.18	89.77 (73.60–96.72)	7964 (67.5)
Difference (Max - Min)		3708	8.7	4.03	992
6. Observation period
a. 1 year		12,620	84.04 ±18.28	91.41 (76.61–97.83)	8998 (71.3)	<0.0001
b. 2 years		13,681	79.27 ±22.56	88.79 (67.77–96.69)	8723 (63.8)
c. 3 years*		14,288	76.70 ±24.59	86.80 (63.05–96.15)	8549 (59.8)
d. 5 years		14,888	74.11 ±26.17	84.56 (58.18–95.49)	8374 (56.2)
e. 8 years		15,171	73.43 ±26.36	83.37 (57.92–95.06)	8277 (54.6)
Difference (Max - Min)		2551	10.61	8.0	721
Category 3: Calculation methods of medication adherence
7. Handling end-date-of-study
a. Prescription-based approach*		14,288	76.70 ±24.59	86.80 (63.05–96.15)	8549 (59.8)	<0.0001
b. Fixed period-based approach		13,950	70.94 ±28.82	82.76 (50.55–95.16)	7417 (53.2)
Difference (Max - Min)		338	5.76	4.04	1132
8. Handling overlaps
a. No carryover was granted		14,222	74.47 ±23.65	84.08 (61.50–92.75)	8096 (56.9)	<0.0001
b. Carryover of overlaps unconditionally*		14,288	76.70 ±24.59	86.80 (63.05–96.15)	8549 (59.8)
c. Carryover of overlaps if a period of overlaps was under 14 days		14,270	75.79 ±24.26	85.52 (62.45–94.83)	8375 (58.7)
d. Carryover of overlaps if prescriptions were issued by the same institution		14,293	76.38 ±24.52	86.34 (62.74–95.74)	8492 (59.4)
Difference (Max–Min)		71	2.23	2.72	453

Note: *The base-case of this study.

Abbreviation: PDCwith≥1, proportion of days covered with one or more medications.

Figure 2 Diverse impacts of measures of medication adherence and rates of adherent patients with varied options on PDCwith≥1.

Notes: Among the eight decision nodes measured, the two choices that had the most impact were handling the end-date-of-study and overlaps in the third category, with few differences in the sample size. Decision node 1. Elimination claims that are irregular (1a: In-hospital medication initiation, 1b: In-hospital medication initiation or use of injectable agents, 1c: Short-term prescribing under 7 days). Decision node 2. Elimination of duplicate claims (2a: Deduplication, 2b: Leave as it was). Decision node 3. Minimum number of prescriptions (3a: At least two prescriptions, 3b: At least four prescriptions). Decision node 4 Pre-index period (4a: 180 days,4b: 365 days, 4c: 730 days). Decision node 5. Minimum cumulative number of days’ supply (5a: 30 days,5b: 90 days, 5c: 180 days, 5d: 1 year). Decision node 6. Observation period (6a: 1 year, 6b: 2 years, 6c: 3 years, 6d: 5 years, 6e: 8 years). Decision node 7. Handling end-date-of-study (7a: Prescription-based, 7b: Fixed period-based). Decision node 8. Handling overlaps (8a: No carryover was granted, 8b: Carryover of overlaps unconditionally, 8c: Carryover of overlaps if a period of overlaps was under 14 days, 8d: Carryover of overlaps if prescriptions were issued by the same institution). *The base-case of this study.

Abbreviation: PDCwith≥1, proportion of days covered with one or more medications.

Table 3 Comparing the Varied Impacts of PDC_wm and DPPR Measures Compared to PDC_with≥1

Decision Node	Case	PDCwith≥1 Median (Q1–Q3)	PDCwm		DPPR
			Median (Q1–Q3)	%Change from PDCwith≥1	Median (Q1–Q3)	%Change from PDCwith≥1
Base-case setting		86.80 (63.05–96.15)	83.59 (59.89–94.92)	−3.70	86.39 (62.58–95.84)	−0.47
Category 1: Definition of data cleaning
1. Elimination claims that are irregular for hypertension medication
Smallest	a. In-hospital medication initiation	85.96 (61.70–95.75)	82.80 (58.66–94.58)	−3.68	85.66 (61.35–95.49)	−0.35
Largest	c. Short-term prescribing under 7 days	86.80 (63.05–96.15)	83.59 (59.89–94.92)	−3.70	86.39 (62.58–95.84)	−0.47
2. Elimination of redundant duplicate claims
Smallest	a. Deduplication	86.80 (63.05–96.15)	83.59 (59.89–94.92)	−3.70	86.39 (62.58–95.84)	−0.47
Largest	b. Leave as it was	87.37 (63.48–96.47)	84.03 (60.29–95.17)	−3.82	86.98 (62.99–96.13)	−0.45
Category 2: Inclusion criteria and observation period
3. Inclusion criteria for a minimum number of prescriptions
Smallest	a. At least two prescriptions	86.80 (63.05–96.15)	83.59 (59.89–94.92)	−3.70	86.39 (62.58–95.84)	−0.47
Largest	b. At least four prescriptions	86.81 (63.39–96.12)	83.59 (60.23–94.85)	−3.71	86.40 (62.92–95.79)	−0.47
4. Inclusion criteria for pre-index period
Smallest	a. 180 days	85.68 (61.50–95.87)	82.27 (58.10–94.49)	−3.98	85.29 (61.01–95.52)	−0.46
Largest	c. 730 days	87.51 (64.13–96.34)	84.38 (61.09–95.13)	−3.58	87.15 (63.79–96.00)	−0.41
5. Inclusion criteria for supply for the minimum cumulative number of days
Smallest	a. 30 days	85.74 (59.14–96.05)	82.36 (55.92–94.77)	−3.94	85.33 (58.64–95.71)	−0.48
Largest	d. 1 year	89.77 (73.60–96.72)	86.73 (69.46–95.71)	−3.39	89.48 (73.17–96.44)	−0.32
6. Observation period
Smallest	e. 8 years	83.37 (57.92–95.06)	76.22 (52.19–91.86)	−8.58	82.97 (57.59–94.75)	−0.48
Largest	a. 1 year	91.41 (76.61–97.83)	90.12 (74.28–97.07)	−1.41	90.93 (76.08–97.33)	−0.53
Category 3: Calculation methods of medication adherence
7. Handling end-date-of-study
Smallest	b. Fixed period-based approach	82.76 (50.55–95.16)	79.10 (48.08–93.80)	−4.42	82.44 (50.09–94.89)	−0.39
Largest	a. Prescription-based approach	86.80 (63.05–96.15)	83.59 (59.89–94.92)	−3.70	86.39 (62.58–95.84)	−0.47
8. Handling overlaps
Smallest	a. No carryover was granted	84.08 (61.50–92.75)	81.06 (58.07–91.76)	−3.59	83.73 (61.00–92.56)	−0.42
Largest	b. Carryover of overlaps unconditionally	86.80 (63.05–96.15)	83.59 (59.89–94.92)	−3.70	86.39 (62.58–95.84)	−0.47

Abbreviations: PDCwith≥1, proportion of days covered with one or more medications; PDCwm, duration weighted mean PDC; DPPR, daily polypharmacy possession ratio.