Journal of the National Institute of Public Health2014 Vol.63 No.6 p.532−537

Topic： Application of DPC data for evidence-based health policy＜Note＞
Estimation of per-case hospitalization charges from
Diagnosis-Procedure-Combination (DPC) data and an international
comparison of hospital prices
Etsuji OKAMOTO, Toshiro KUMAKAWA
National Institute of Public Health
Abstract
Objectives: OECD launched a project to compare price levels of hospital charges internationally usingpurchasing-power-parity (PPP). The comparison is made for seven disease categories from internal
medicine, 21 surgical procedures and four day-surgeries using per-case charges covering admission todischarge. The results of a pilot study in 16 countries are already published. To obtain Japan’s data, theper-case hospital charges of said categories and procedures were estimated and compared with theresults of the pilot study.
Methods: The per-case hospital charges were estimated from the “survey on the effects of theintroduction of DPC (diagnosis-procedure-combination) reimbursement” by applying log-normal
distributions to the 25th, 50th, 75th and 90th percentiles of length-of-stay (LOS). Surgical procedures
and anesthesia are reimbursed on a fee-for-service basis and surgical charges were added to theestimated hospital charges.
Results: Comparison was made in terms of seven disease categories from internal medicine and 17
surgical procedures. Japan was ranked as most expensive for cholelithiasis (top among 15 countries)
and least expensive for PTCA (percutaneous transluminal coronary angioplasty) (11th among 17
countries). Japan was ranked above the middle in 17 out of 24 categories/procedures.
Conclusions: Japan’s hospitals were rather expensive among OECD countries due mainly to theexcessively long LOS. Japan’s LOS was longest in 19 out of 24 categories/procedures. Japan was ranked
4th among 11 countries even for its shortest LOS of angina).
keywords: hospital charges, diagnosis-procedure-combination (DPC), length-of-stay, log-normal
distribution(accepted for publication, 3rd November 2014)

I.

Objectives

OECD is conducting the “Hospital Purchasing-PowerParity (PPP) survey” to develop the internationallycomparable price indices of hospitalization. Hospitalization
charges are all-inclusive charges including room andboard, medication and laboratory, surgery and anesthesia
covering the entire length of stay from hospitalization todischarge. They are difficult to measure particularly incountries with wide variety of length of stay. Japan’s
length of stay is the longest among OECD countries andestimation of hospitalization per-case charges is amethodological challenge.
We attempted to estimate the hospitalization charges
using Diagnosis-Procedure-Combination (DPC) data by
applying a statistical model of log-normal distribution andcompared the estimated per-case hospital prices with 12
OECD countries from the pilot study.

Corresponding Author: Etsuji Okamoto
2-3-6, Minami, Wako, Saitama, 351-0197, Japan.
T e l: +81-48-458-6208
E-mail: atoz@niph.go.jp

532

J. Natl. Inst. Public Health, 63（6）: 2014

Estimation of per-case hospitalization charges from Diagnosis-Procedure-Combination (DPC) data and an international comparison of hospital prices with OECD countries

II. Data and Methods
1．OECD hospital survey
OECD launched an international comparative survey
on hospital charges in 2008 and the results of the pilot
study on 12 participating countries is published [1]. It
collects the charges billed for certain “defined”
hospitalization (case types). To achieve international
comparability, the charges are compared using purchasing
power parity or PPP, a common tool for comparing pricelevels across countries.
Case types include nine medical inpatient services(IM01-09) and 23 surgical inpatient services (IS02-24).
Medical services are defined by primary diagnoses andsurgical services are defined by surgical procedures.
2．Japan’s DPC classification
DPC is a Japan’s patient classification system for acutecare hospitalization consisting of 2658 categories in 2010
fee schedule, of which 1875 DPCs were reimbursed on a
per-diem basis (DPC per-diem payment system or DPCPDPS). DPC-PDPS are selected from categories with
sufficient sample size (N>＝20) and patients classified
into the rest of DPCs will be reimbursed on a traditional
fee-for-service (FFS) basis.
PDPS bundles room and board, medication andinjection, clinical procedures priced less than 20000 yen.
It does not include surgery and anesthesia, which will bebilled separately. PDPS is staged at three levels by thelength of stay. There is a maximum on the LOS andprolonged hospitalization beyond the maximum LOS will
be reimbursed on a traditional FFS.
There were a total of 7,528 acute somatic hospitals with
899,385 acute care beds as of October 2011 according to
the Health Care Facilities Survey, of which 1,634
hospitals with 491,282 beds are assigned as DPC wards.
There were a total of 8,777,507 discharges from DPC
wards, of which 8,310,372 discharges (94.7%) were
reimbursed on PDPS for one year between April 2011
and March 2012.
Data of DPC-PDPS (1825 DPCs, N=8,310,372) areavailable over the Ministry of Health, Labour & Welfare
website [2] and includes the following:
1) the number of discharges in each DPC broken down by:(1)sex(2)age groups (in eight categories: 0-2, 3-5, 6-15, 16-20,
21-40, 41-60, 61-79 and 80 or over)(3)prognoses at discharge (in eight categories: cured,
alleviated, improved, no change, exacerbated, death
due to the most resource-intensive diagnosis, death
due to other diagnoses, and others)(4)the most resource-intensive diagnosis classified by
ICD10(5)types of surgery provided if any (in Japan’s local
surgery code called Kcode)2) distribution of length of stay (LOS)(1)minimum, maximum, arithmetic mean, coefficientof variance(2)25th, 50th, 75th, 90th percentiles
A simplest way of calculating charges for a
hospitalization would be to break the arithmetic mean of
LOS into three stages and multiply with per-diem
reimbursement prices. For example, a DPC 010010xx010xx(Brain tumor with no surgery) will be reimbursed 2878
points for the first 10 days, 2127 points between 11th and21st days and 1808 points for the LOS over 22nd day.
There was a total of 7469 cases and the arithmetic meanof LOS was 23.58 days. Then, the charge of a
hospitalization can be calculated by 2878 points×11 days
＋2127 points×10 days＋1808 points×2.58 days＝57592.64
points.
Historically, Japan’s health insurance system fixed thepoint charge at 10 yen. However, in DPC, each hospital isassigned different level of point charge ranging from thelowest of 8.922 yen to the highest of 13.556 yen. The
eventual price ranges from the lowest of 513,841 yen to
the highest of 780,726 yen for exactly the same case.
However, such a simple calculation is likely tooverestimate the charges because the LOS is notnormally distributed. The distribution of LOS is known tobe skewed to right because a small number of patientsstay exorbitantly long (The maximum LOS of this DPC
was 220 days).
In this study, we applied log-normal distribution tobetter estimate per-case charges.
3．Method
Log-normal distribution functions were estimated foreach of DPCs (N=1875) using the 25th, 50th,75th and90th percentiles LOS (X). Log-normal functions are
determined by geometric mean (GM, arithmetic mean of
LN(X)) and geometric standardized deviation (GSD,
standard deviation of LN(X)). GM and GSD were
estimated using Excel Solver to minimize the sum ofsquares of the differences between the observed
percentile LOS and estimated percentile LOS.
Let the observed 25th, 50th, 75th and 90th percentiles
LOS be expressed as LOS0.25, LOS0.5, LOS0.75 and LOS0.9
respectively. Further, the estimated percentile LOS using
an Excel function, LOGINV, is expressed as
LOGINV(0.25, GM, GSD), LOGINV(0.5, GM, GSD),
LOGINV(0.75, GM, GSD) and LOGINV(0.9, GM, GSD)
respectively (LOGINV is an Excel function to give X
value of a log-normal distribution of given GM, GSD andcumulative probability, p and is expressed as X＝
LOGINV(p, GM, GSD)):
GM and GSD were estimated to minimize the following

J. Natl. Inst. Public Health, 63（6）: 2014

533

Etsuji OKAMOTO, Toshiro KUMAKAWA

sum of squares
i) probability of hospitalization on the Xth day
Once GM and GSD were estimated, the probability of apatient being hospitalized for a length of X days isexpressed by a probability function of the estimated lognormal distribution and the probability of a patient being
hospitalized for a length of one to X days is expressedby a cumulative probability function of log-normal
distribution. Then, the probability of a patient hospitalizedon the Xth day is expressed as 1-cumulative
probability(X-1) because patients whose LOS is X-1 daysor less are discharged before the Xth day. Using an
Excel function, it is expressed as:
1-LOGNORMDIST(X-1,GM,GSM)ii) estimation of per-case charges
Let the per-diem price of DPC on the Xth day be Hx
then the total price of a hospitalization of a given DPC is(max is the maximum LOS of each DPC):

peripheral abscess
K718-22 Laparoscopic appendectomy with peripheralabscess
The above KCODEs are performed in a total of 48,598
cases spreading over 38 DPCs, of which DPC“060150xx02xx0x” accounts for 38,605 cases (79.4%)
followed by “060150xx02xx1x” with 8,440 cases (17.4%).
The first six digits denote the most resource-intensive
diagnosis: “060150”, “appendicitis” and the last but one
digit from right: ‘0’ and ‘1’, denotes the absence/presenceof secondary diagnoses. The total cases of these two
DPCs were 39,211 and 8,790 respectively. Although
appendectomy is by far the most common procedures
performed on patients with appendicitis, some of themare performed with different surgical procedures such as
surgeries for acute pan-peritonitis. Since OECD defines
surgical cases based on types of surgical procedures, percase price as well as average length of stay of 38 DPCs
had to be collated using the number of appendectomy asweight (actually the least frequent 13 DPCs had only one
appendectomy each).

III. Resultsiii) estimation of average point charges
Reimbursement rate of DPC is expressed in points andmust be multiplied with point charge to translate it into
yen amount. Historically, Japan’s health insurance system
has fixed a point at 10 yen. However, in DPC system,
each hospital is assigned a different point charge. The
average point charge was estimated by weighted averageof entire hospitals (N=1,634) using the number of DPC
cases as weight.
iv) estimation of surgical charges
DPC does not include surgery and anesthesia and they
are reimbursed separately on a fee-for-service basis(point charge is set at 10yen). Surgical fees were
estimated separately from DPC database. The DPC
database included the number of cases for which
surgeries are performed by Japan’s local surgical coding(KCODE).
For example, appendectomy is defined by the following
ICD-9-CM coding:
47.01 Laparoscopic appendectomy
47.09 Other appendectomy
47.11 Laparoscopic incidental appendectomy
47.19 Other incidental appendectomy
The above ICD-9-CM coding is translated into thefollowing Japan’s KCODE
K718-01 Appendectomy without peripheral abscess
K718-02 Appendectomy with peripheral abscess
K718-21 Laparoscopic appendectomy without

534

The average point charge was estimated as 10.96 yen
per point. The total charges of DPC-PDPS cases (N＝8,310,372) was estimated to be 3.756 trillion yen or
451,981 yen per discharge (US$4520 when $1＝￥100).
The results of the number of cases, average length ofstay (ALOS) and hospitalization prices converted into
US$ ($1=￥100) are presented in [Table1], [Table2] and[Table3] respectively incorporating the results from 12
OECD countries to allow international comparison. In[Table2] and [Table3], the ranking of Japan in OECD
countries which provided data is also included.
As for ALOS, Japan is known as a country with thelongest ALOS. True, Japan ranked as the 1st in 19 of 24
case types. It is noteworthy that Japan’s ALOS is shorter
than US in inguinal hernia repair. As for prices, Japanranks in the upper half of OECD countries in most casetypes. It is noteworthy that Japan’s hospital is more
expensive than US in three internal medicine case types:
cholelithiasis, heart failure and pneumonia. This may be
explained by Japan’s long ALOS.

IV. Discussion
Analyzing DPC data, we were able to provide
internationally comparable prices of hospitalization ofJapan. So far, Japan has not been used to capture theprice of an entire hospitalization from admission todischarge.
Our findings revealed that Japan’s hospitals occupy
higher end of the price lists of OECD countries. Japan’s

J. Natl. Inst. Public Health, 63（6）: 2014

Estimation of per-case hospitalization charges from Diagnosis-Procedure-Combination (DPC) data and an international comparison of hospital prices with OECD countries
Table 1 The number of cases (2011 for Japan, 2007 for other countries)
Code Case
IM01 Acute myocardial infarction
IM02 Angina pectoris
IM03 Cholelitiasis
IM04 Heart failure
IM06 Malignant neoplasm of breast
IM07 Malignant neoplasm of bronchus and lung
IM09 Pneumonia
IS02 Appendectomy
IS03 Caesarean section
IS04 Cholecystectomy
IS05 Colorectal resection
IS06 Coronaryartery bypass graft
IS08 Discectomy
IS09 Endarterectomy:vessels of head and neck
IS12 Hipreplacement:total and partial
IS13 Hysterectomy:abdominal and vaginal
IS14 Knee replacement
IS16 Mastectomy
IS17 Open prostatectomy
IS19 Percutaneous transluminal coronary angioplasty (PTCA)
IS20 Peripheral vascular bypass
IS22 Repair of inguinal hernia
IS23 Thyroidectomy
IS24 Transurethral resection of prostate (TURP)
TOTAL

AUS
CAN FINFRAGERISR
ITA KOR NOR POR SLV SWE
USA
JPN
23339 17698 2013
1304
74481
5737 3840 15727
7701 1447 15015 297521
7246
37865
3258 1070
1892
4613 1642
3227 1834
9980
23417 187701
16830
5076
648
3684
22351
9848 2477
6471 5295
6628 1657
4883
76382
22258
33361 29950 2210 19826 269216 37022 10081
8856 8998 14610 3106 19667 774790 169430
2336
356
628
1665
53763
2960
311 28533 3130
1044 2656
1998
7534
34969
13014
3699
761
8255 152450
3193 2387 43279 8621
4163 1194
4416
79434 189905
60288 35922 4333 19038 221028 27201 8827 170652 26056 38131 3918 22885 1046752 253890
20439 24433 1786
6108 100634
7756 3010 69089 4760 11050 1839
8880 293502
48598
55556 74972 3204 13467 198385 22905
41 113534 9671 27306 2790 17991 1451359
53053
25044 19589 1233
7613 153563
5922 4646 20626 6383 15880 4216
7460 372598 103663
10595 21077
570
4043
3381 1428
4860
7350
1
5110 280959
91514
4388 10733
439
2656
28494
2699
732
1899 2873
2630
528
3730 192107
14886
962
4853 1298
2945
924 2446 40052
2630
513
3999 123387
18535
1819
2532
77
40
728 1289
111
503
124
892 113390
18535
13810 26727 1748
8335 159220
2172 5484 29949
7707 3057 18296 384497
28748
14203 32999 1420
4301
82337
2801
333 24940
11017 1082
7228 508943
55976
11699 36017 1260
2865 140812
1892 1869 21173
4655 1255
8987 585500
29544
8567
7012
686
3239
725
414
6730 1316
2771
273
1917
68211
61965
16226
7159
177
2467
1077
118
147
2657
269
2467
86974
17391
17276 17459
463 13267
10365 10362 6842
4268 10300
7579 1097 15254 660217 243024
4389
3282
320
803
1077
924
793
1138
66
583
61568
10995
17187 10633
887
7139
8087 1582 25288 2183 14333 3392
3917
32330 105190
4162
8006
467
5175
1333
281 17231 1125
4677
200
2123
46917
22455
9071 13342
575
2570
58588
1714 1916
2940 4103
2330
537
4869
68241
21645
422426 416784 28273 142697 1725687 166129 62920 657148 94814 201717 37051 192547 7636530 1811116

Table 2 Hospitalization prices in US dollars (2011 for Japan, 2007 for other countries, $1＝\100)
Code Case
IM03 Cholelitiasis
IM04 Heart failure
IM09 Pneumonia
IS17 Open prostatectomy
IM07 Malignant neoplasm of bronchus and lung
IS13 Hysterectomy:abdominal and vaginal
IS04 Cholecystectomy
IS08 Discectomy
IS03 Caesarean section
IS05 Colorectal resection
IS16 Mastectomy
IM01 Acute myocardial infarction
IS12 Hipreplacement:total and partial
IS23 Thyroidectomy
IS06 Coronaryartery bypass graft
IS24 Transurethral resection of prostate (TURP)
IM02 Angina pectoris
IS20 Peripheral vascular bypass
IS14 Knee replacement
IM06 Malignant neoplasm of breast
IS09 Endarterectomy:vessels of head and neck
IS22 Repair of inguinal hernia
IS02 Appendectomy
IS19 Percutaneous transluminal coronary angioplasty (PTCA)AUS CAN FIN FRA GER ISR
ITA KOR NOR POR SLV SWE USA JPN
2521
2006 3955 2279 1602
1211 5536 2410 1976 2960 5969 6567
5100
3684 5215 3922 1656 6245 1475 7678 4606 2511 4263 5696 5812
4817
3669 6584 3504 1727 4830
976 8201 3299 2487 4100 5893 5942
7552 7797 7948 9405
3391
4698
5115 5296 10368 13025 8103
5097
3503 4495 3050 1764
1839 7607 3610 2655 6460 9086 5116
7135 5742 3989 6412 4163 2909
2984
2877 2889 7612 7313 6741
5615 6350 4484 6927 3728 3185 5406 3683 11324 4078 2343 5844 10487 6904
14055 6909 5267 5518
6815
4464
6313 3781 8139 8007 6368
7092 4820 4808 5820 3732 2002
1957 10593 1998 3113 6375 7449 5011
16653 14831 11846 17473
7335
7048
10120 7188 15404 17289 10892
5525 5455 4761 6668
3305
3987 7093 3443 2960 5549 9297 4881
4245
5163 5439 4626 3093 8287 1174
6238 3091 4540 7579 4307
15918 11983 10834 11162 8899 7950
9022
10869 7628 11568 17406 9152
6000 5050 4919 4854
2023
2785 7333 3636 2669 6126 7483 4257
21698 22694 23468 23126 14067 15488
16577 32111 17133 12281 21218 34358 20219
5239 4548 4183 4986 3733 2144 5474 2155 6041 2277 2404 4403 6625 4297
2074
3466 3007
1973
3299 1838 2256 3647 1702
19570 14296 18162 14790
9870
8371
10840 6781 14140 16657 8990
14608 9910 9931 12424 10011 8272
9222
10319 7652 10348 14946 9301
3254
3596 3425 2293 1621 7130 1331 6726 4643 1643 4393 6947 2858
9458 8502 8494 11578
10136
6665
8153 4085 10192 8371 6368
3093 4489 2904 3327
1799 5026 1986 5107 2646 1287 4041 8917 2307
5044 5004 3739 4558 2943 1726 5647 1594 5989 3502 2145 4961 7962 3175
7131 9277 5574 7027 3347 7814 10063 10254 7942 8001 3250 9296 14378 5767

Japan’s rank
1th in 15
3th in 16
3th in 16
4th in 14
4th in 15
4th in 15
4th in 17
6th in 14
6th in 16
7th in 14
7th in 15
8th in 15
8th in 15
8th in 15
8th in 16
8th in 17
9th in 12
9th in 14
9th in 15
9th in 16
10th in 14
10th in 16
10th in 17
11th in 17

Table 3 Average length of stay (2011 for Japan, 2007 for other countries)
Code Case
IS05 Colorectal resection
IS08 Discectomy
IS17 Open prostatectomy
IS20 Peripheral vascular bypass
IM01 Acute myocardial infarction
IS12 Hipreplacement:total and partial
IS13 Hysterectomy:abdominal and vaginal
IS14 Knee replacement
IS23 Thyroidectomy
IM03 Cholelitiasis
IM04 Heart failure
IM07 Malignant neoplasm of bronchus and lung
IM09 Pneumonia
IS02 Appendectomy
IS03 Caesarean section
IS04 Cholecystectomy
IS06 Coronaryartery bypass graft
IS19 Percutaneous transluminal coronary angioplasty (PTCA)
IS24 Transurethral resection of prostate (TURP)
IS09 Endarterectomy:vessels of head and neck
IS16 Mastectomy
IS22 Repair of inguinal hernia
IM06 Malignant neoplasm of breast
IM02 Angina pectoris

AUS
11.96
7.96
4.79
7.27
4.35
9.40
4.02
7.18
2.30
3.04
6.41
5.86
5.68
2.97
4.84
2.83
9.38
3.32
3.58
5.15
2.92
1.35
3.65
2.32

CAN FIN
10.85 8.40
2.67 3.40
3.51 5.94
9.94 8.79
6.25 5.22
6.99 5.96
3.01 2.15
4.69 5.28
1.90 1.74
3.79 3.14
7.32 7.03
10.67 6.52
5.83 6.12
3.16 2.29
3.29 4.73
4.11 2.83
10.05 9.06
3.94 2.99
2.93 3.40
3.12 3.77
2.04 2.43
2.73 1.80
10.65 4.41
2.68 4.05

FRA
18.05
5.66
9.33
16.97
7.12
12.89
6.41
11.22
3.75
6.15
9.16
6.86
9.73
5.15
7.67
7.12
15.00
5.13
6.83
9.59
6.82
3.46
4.68
4.07

GER

7.80
14.00
7.00
14.10
5.10
10.70
6.10
9.30
4.90
7.20
6.70
11.70
4.00
7.70

4.00

ISR
11.09
4.18
7.31
11.85
5.46
8.78
5.59
8.09
3.89
3.80
4.19
4.03
4.41
3.26
5.08
3.23
10.65
3.70
4.35
5.06
4.06
1.82
3.78
3.03

ITA
13.80
4.79
5.11
9.73
8.27
10.85
5.05
9.38
3.58
7.27
8.46
10.70
9.59
4.45
6.90
5.44
13.05
5.58
5.06
4.52
4.64
3.97
10.16
4.48

KOR NOR
16.94
11.79
13.99
17.87
4.47
20.36
7.30
20.05
6.69 3.60
5.64 3.98
8.51 5.80
6.00 6.90
6.77 6.64
5.85 2.92
6.65 6.00
7.93 4.20
15.45 9.05
9.39 2.45
7.30 3.83
20.42
11.48 4.36
5.71 2.35
4.21 4.83

J. Natl. Inst. Public Health, 63（6）: 2014

POR
16.20
5.96
9.12
21.18
8.48
12.35
5.93
10.47
3.92
7.01
9.57
12.46
10.63
4.91
4.61
6.20
12.81
6.01
6.85
8.27
6.97
2.82
8.16
1.76

SLV SWE USA JPN Japan’s rank
21.00 9.60 9.76 25.04
1st in 12
8.14 4.44 2.15 18.36
1st in 1211.67 4.32 2.42 17.05
1st in 1214.82 7.72 7.19 24.23
1st in 126.50 4.25 4.41 12.38
1st in 13
12.23 7.22 4.67 28.83
1st in 13
9.00 4.00 2.57 12.72
1st in 13
11.47 6.00 3.64 29.86
1st in 13
3.64 1.86 1.88 10.05
1st in 13
4.96 2.97 3.72 11.30
1st in 148.76 5.13 4.93 22.08
1st in 14
4.12 7.80 6.42 15.15
1st in 14
7.43 4.61 4.88 13.21
1st in 14
4.94 2.40 2.74 7.83
1st in 14
8.30 3.95 3.60 13.48
1st in 14
4.62 2.42 4.57 14.97
1st in 1414.66 7.33 9.36 29.68
1st in 14
4.79 2.54 2.70 10.28
1st in 14
8.03 2.66 3.04 10.72
1st in 14
8.18 3.91 2.55 18.36 2nd in 12
9.82 2.36 2.21 10.11 2nd in 13
2.90 1.66 7.23 6.84 2nd in 13
1.96 5.93 5.85 8.61 3rd in 14
3.14 1.96 1.94 3.80
4st in 11535

Etsuji OKAMOTO, Toshiro KUMAKAWA

length of stay is still long and it is considered to be amajor reason why Japan’s hospitals are more expensive
than OECD standards. These results suggest that Japan’s
hospitals need more efficiency through shortening thelength of stay.
There are some limitations to this study. The data year
was 2011 while the data of other countries were of 2007.
This was inevitable because DPC participating hospitals
were not as many as they are today. Also in that year, only
six months data were collected. For the first time in
FY2011, data covering an entire year were collected from1,634 DPC participating hospitals. The sheer sample sizeof 8,310,372 discharges is only second to the US andalmost comparable to Germany according to [Table1]
making it sufficiently large to enable international
comparison.
Another limitation is that prices are converted into US$
under the current exchange rate ($1=￥100) and isamenable to the fluctuation of exchange rate. OECD
advocates using PPP for international comparison
incorporating consumer prices. Unfortunately, we did not
attempt to calculate PPP in this study.
And, most importantly, DPC data do not cover theentire Japan’s acute admissions. Only acute care
hospitals fulfilling certain requirements (such as thenumber of medical and nursing staff per bed) arepermitted to use PDC PDPS. Still, nearly half of acute536

care admissions occur in non-DPC hospitals, one cannot
generalize the findings from DPC data to the entire
country.
Despite the above limitations, our estimates of per-case
hospital charges are pioneering in nature and will bringabout various implications for not only international
comparison but also for domestic health policy
development.

Acknowledgement
The content of this article was presented at the 9th
Annual Meeting of Japan Health Economics Association(JHEA) on 6th September 2014 (Tokyo).

References[1] Koechlin F, Lorenzoni L, Schreyer P. Comparing
Price Levels of Hospital Services Across Countries.
OECD Health Working Papers. 2010;53:60. http://dx.
doi.org/10.1787/5km91p4f3rzw-en (accessed 201411-03)[2] Ministry of Health, Labour & Welfare. The survey
on the effects of the introduction of DPC.
http://www.mhlw.go.jp/stf/shingi/2r9852000002hs9l.
html (accessed 2014-11-03)

J. Natl. Inst. Public Health, 63（6）: 2014

Estimation of per-case hospitalization charges from Diagnosis-Procedure-Combination (DPC) data and an international comparison of hospital prices with OECD countries

DPCデータを用いた入院費用の推計と，OECD加盟国との価格比較
抄録
目的：OECDは病院費用を疾患別に国際比較するプロジェクトを開始した．９内科疾患，２３外科
手術，４日帰り手術について入院から退院までの総費用を推計し，購買力平価（PPP）で比較するもので，２０
１０年に１６か国で実施されたパイロット調査の結果が公表済であり，２０１
３年より本調査が開始された．DPC調査を用いて，わが国急性期病院の疾患別入院費用を推計し，パイロット調査されたOECD加盟国の価格と比較する．
方法：２０
１１年度DPC導入の影響調査結果より在院日数の２
５，５
０，７
５，９
０％タイル値に対数正規分布を適用し，１８７
５DPC毎の入院から退院までの包括点数の平均を算出した（一点単価は医療機関
別 係 数 に 病 院 毎 の 症 例 数 を 加 重 平 均 し た１
０９. ６円）
．内 科 疾 患 に つ い て は 医 療 資 源 投 入 病 名（ICD１０）よりOECD指標の対象疾患を抽出しDPC平均点数を症例数で加重平均した．外科系疾患については実施された手術（K）コード数で加重平均し手術と麻酔点数を加えた．得られた疾患別，手術別入院費用を米ドル換算してパイロットスタディ参加国と比較した（パイロットスタ
ディでは物価補正したPPPは算出されず）．
結果：７内科疾患と１
７外科手術を比較できた．わが国順位が最も高かったのは胆石症で１
５か国中１位，最も低いのはPTCAで１７か国中１１位であった．２
４疾患・手術中１
７でわが国は中位より上であった．
結論：公表されている（算術）平均在院日数で算出したらわが国は突出した高額だったため，対数正規分布を適用し幾何平均を用いたが，それでもわが国入院費用はOECD加盟国中高額の部類であった．その最大要因はわが国の在院日数の長さであり，２
４疾患・手術中１９でトップであった（最も短かったのは狭心症で１
１か国中４位）．
キーワード：病院費用，DPC（診断群分類），在院日数，対数正規分布
岡本悦司，熊川寿郎
国立保健医療科学院

J. Natl. Inst. Public Health, 63（6）: 2014537