Case-mix Analysis Across Patient Populations and Boundaries: A Refined Classification System
Designed Specifically for International Quality and Performance Use
A white paper by:
— Marc Berlinguet, MD, MPH
— James Vertrees, Ph D
— Richard Freedman, Ph D
— Rachael D’ Andrea, RHIA, CPHQ
— Ann Tinker, RN, MN
Abstract
T h is p a p e r d e s c r ib e s th e s tr u c tu r e a n d f e a tu r e s o f th e 3 M™ I n te r n a tio n a l Re f in e d - D RG s ( I RD RG s ) a n d a s s e s s e s th e v a lid ity o f a n e w a p p r o a c h to s ta n d a r d iz in g th e d e f in itio n s o f
h o s p ita l in p a tie n t a n d a mb u la to r y p r o d u c ts . T h e c lin ic a l r e s e a r c h e r s a t 3 M H e a lth
I n f o r ma tio n S ys te ms r e c o g n iz e c o u n tr ie s n e e d D RG s c a p a b le o f d e s c r ib in g a n d v a lu in g
i n p a t i e n t a n d o u t p a t i e n t s er v i c e s a n d s u p p o r t i n g t h e u se o f p e r f o r ma n c e a n d q u a l i t y
in d ic a to r s . I n a d d itio n , f o r in te r n a tio n a l u s e , it is imp o r ta n t to r e c o g n iz e th a t c o u n tr ie s a ls o
require:
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A f le x ib le p a tie n t c la s s if ic a tio n s ys te m to c a p tu r e f e a tu r e s u n iq u e to th e c o u n tr y
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T h e a b i l i t y t o c o mp a r e o n e c o u n t r y t o a n o t h e r
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T h e a b i l i t y t o e n c o u r a g e t h e p r o v is i o n o f c a r e i n a n a mb u la t o r y s e t t i n g , w h e r e
me d ic a lly a p p r o p r ia te
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T h e a b i l i t y t o a d j u s t f o r d if f e r e n c e s i n i n p a t i e n t s e v e r i t y o f i l l n e s s , a n d
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T h e a b i l i t y t o c o mp a r e h o s p i t a l s i n t e r ms o f o u tc o me s s u c h a s mo r t a l i t y
F o r th e s e r e a s o n s , 3 M H I S h a s d e s ig n e d th e I R- D RG s :
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U s i n g t e c h n o l o g i e s t h a t f a c i l i t a t e l oc a l i z a t i o n t o i n d iv i d u a l c o u n t r i e s
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T o b e c o d e in d e p e n d e n t, i. e . , to p r o v id e t h e s a me r e s u l t s i n c l a s s i f y i n g p a t i e n ts ,
r e g a r d l e s s o f t h e c o d in g s y s t e ms u s e d , t h e r e b y f a c i l i t a t i n g i n t e r n a t i o n a l c o mp a r i s o n s
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T o d e s c r ib e b o th in p a tie n t a n d a mb u la to r y e n c o u n te r s in o n e s e a mle s s s ys te m
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T o c o n s i s t e n t l y u s e t h e c o n c e p t o f s e v e r i t y a d j u s t me n t t o b e t t e r d e s c r i b e r e l a t i v e
r e s o u r c e c o n s u mp tio n b a s e d o n in d iv id u a l p a tie n t c h a r a c te r is tic s , a n d
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T o in c lu d e o u tc o me in d ic a to r s :
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Risk of Mortality (ROM) (2008)
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P o t e n t i a l l y P r e v e n t a b le R e a d mis s i o n s ( P P R s ) ( p l a n n e d )
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P o t e n t i a l l y P r e v e n t a b le C o mp l i c a t i o n s ( P P C s ) ( p l a n n e d )
T h e w o r ld w id e in f o r ma tio n r e v o lu tio n h a s c a ta lyz e d imp r o v e me n ts to h o s p ita l d a ta
s y s t e ms u s i n g c a s e - mix a n a l y s i s f o r d e c is i o n s u p p o r t i n r e s o u r c e u t i l i z a t i o n a n d
h e a lth c a r e f u n d in g a r r a n g e me n ts . E s s e n tia l to th is e f f o r t is th e u s e o f a s o p h is tic a te d
s y s t e m f o r c l a s s i f yin g a n d e v a lu a tin g c o mp le x h e al t h c a r e i n f o r ma t i o n . H e a l t h c a r e
d e c is io n - ma k e r s r e q u ir e a me a n s o f ma k in g r e la tiv e c o mp a r is o n s o f th e s e r v ic e s a n d
r e s o u r c e s p a t i e n t s c o n s u me a n d t h e i r c o r r e s p o n d i n g q u a l i t y a n d p e r f o r ma n c e . A
s in g le p a tie n t c la s s if ic a tio n s ys te m th a t e n c o mp a s s e s a w id e v a r ie ty o f c o d in g
s y s t e ms a n d c l i n i c a l p r a c t i c e s i n b o th i n p a t i e n t a n d a mb u la t o r y s e t t i n g s w i l l a l l o w f o r
a c c u r a t e b e n c h - ma r k i n g a n d u t i l i z a t i o n as s e s s me n t , i n a d d i t i o n t o p r o v i d i n g a n
accurate basis for healthcare funding and budgeting.
S ig n if ic a n t s h if ts in th e ma n a g e me n t o f h e a lth c a r e d e liv e r y a r e o c c u r r in g a r o u n d th e
w o r ld . T h e r e a r e a n in c r e a s in g n u mb e r o f n o n - g o v e r n me n t- o w n e d d e liv e r y s ys te ms
in v o lv e d in p r o v id in g h e a lth c a r e to p o p u la tio n s th a t w e r e e ith e r p r e v io u s ly ma n a g e d
b y o r e x c lu d e d f r o m g o v e r n me n t- f u n d e d n a tio n a l h e a lth p r o g r a ms . E c o n o mic
p r e s s u r e s a r e f o r c i n g a l l o f t h e s e d e l i v e r y mo d e ls to d e s c r ib e , in a u n if o r m f a s h io n ,
r e s o u r c e u t i l i z a t i o n a n d o u tc o me p a t t e r n s t o b e t t e r ma n a g e r e s o u r c e s w h i l e
f a c i l i t a t i n g i mp r o v e me n ts i n q u a l i t y o f c a r e . 1 A s mo r e g o v e r n me n ts a n d o th e r
e n t i t i e s a r e a s k e d t o ma k e d e c i s i o n s r e g a r d i n g t h e p r o v is i o n o f h e a l t h c a r e , t h e r e i s
a n i n c r e a s e d n e e d f o r h e a l t h c a r e i n f o r ma t i o n a n d t h e r e a l iz a tio n o f th e imp o r ta n c e o f
d e v e l o p in g a p p r o p r i a t e , c o mmo n me a s u r e s o f h o s p i t a l a c t i v i t y t o f u l l y u t i l i z e
D ia g n o s is Re la te d G r o u p s ( D RG s ) o r o th e r c la s s if ic a tio n s ys te ms . A n a p p r o p r ia te
s ys te m th a t is r e le v a n t to a c o u n tr y’ s s p e c if ic n e e d s is r e q u ir e d to c a te g o r iz e th e
p a t i e n t s t h e s e h e a l t h c a r e s y s t e ms ma n a g e .
Issues
A s t a t i s t i c a l l y v a l i d a n d c l i n i c a l l y c o h e r e n t s y s t e m mu s t b e e mp l o y e d t o a g g r e g a t e
p a tie n t d ia g n o s is a n d /o r tr e a tme n t e p is o d e s th a t a r e s imila r in th e ir r e s o u r c e
c o n s u mp tio n a n d to e x p la in v a r ia tio n s i n r e s o u r c e u s e . C l a s s i f i c a t i o n s y s t e ms
d e v e lo p e d f o r th e U n ite d S ta te s a n d o th e r c o u n tr ie s c a n b e d if f ic u lt to a d a p t w h e r e
p r a c tic e p a tte r n s a n d c o d in g s ys te ms v a r y f r o m th e d a ta u s e d in th e d e v e lo p me n t o f
t h e s y s t e ms . I t i s a p p a r e n t t h a t s u c h s y s t e ms a r e l i mi t e d i n t h e i r a b i l i t y t o f u l l y me e t
th e n e e d s o f o th e r c o u n tr ie s . P r e s e n tly, n u me r o u s c o d in g a n d c la s s if ic a tio n s ys te ms
a r e u s e d w o r ld w id e . Ma n y c o u n tr ie s h a v e a d o p te d th e W o r ld H e a lth O r g a n iz a tio n ’ s
I n te r n a tio n a l Cla s s if ic a tio n o f D is e a s e s 1 0 th r e v is io n ( W H O I CD - 1 0 ) . Ma n y c o u n tr ie s
h a v e a ls o d e v e lo p e d o r mo d if ie d th e ir e x is tin g p r o c e d u r e c o d in g s ys te ms .
H o w e v e r , a c o mmo n p r o c e d u r e c o d i n g s y s t e m i s s t i l l n o t w i d e l y u s e d , s o c o u n t r i e s
c o n tin u e to a d a p t e x is tin g s ys te ms o r d e v e lo p c o u n tr y- s p e c if ic p r o c e d u r e c o d e s .
A s th e u s e o f v a r io u s c o d in g s ys te ms in c r e a s e s , p a tie n ts w h o e x h ib it s imila r c lin ic a l
a n d r e s o u r c e c o n s u mp tio n c h a r a c te r is tic s — r e g a r d le s s o f th e c o u n tr y th e y a r e tr e a te d
i n — n e e d t o b e c l a s s i f i e d i n a u n i f o r m a n d c o n s is te n t w a y. A s a r e s u lt o f th e
i n c r e a s e d a v a i l a b i l i t y o f r e l i a b le d a t a , t h e i n f o r ma t i o n d e r i v e d f r o m t h e d a t a n e e d e d
t o d e v e l o p a n i n t e r n a t i o n a l c l a s s i f i c a t i o n s y s t e m h a s r e a c he d a p o i n t o f q u a n t i t y a n d
q u a l i t y t h a t a l l o w s t h i s g o a l t o b e a c h i e v e d . H o w e v e r , n u me r o u s p r o b le ms o c c u r w h e n
a s ys te m o r ig in a lly d e v e lo p e d f o r o n e c o u n tr y is a d a p te d f o r a n o th e r c o u n tr y w h e r e a
d if f e r e n t c o d in g s ys te m is u s e d .
I d e a l l y , a s i n g l e c l a s s i f i c a t i o n s ys te m s p e c if ic a lly d e s ig n e d f o r u s e w ith th e s e v a r io u s
c o d in g s ys te ms c o u ld s o lv e th e s e p r o b le ms . A s c o u n tr ie s c o n tin u e to s h if t to I CD - 1 0 ,
th e id e a l c la s s if ic a tio n s ys te m w o u ld a ls o g r o u p a p a tie n t in to th e s a me D RG
r e g a r d le s s o f th e c o d in g s ys te m u s e d . T h is w o u ld ma k e th e p r o c e s s o f c h a n g e mu c h
e a s ie r f o r h o s p ita l ma n a g e r s .
Answers
I R- D RG s b u ild u p o n k e y d e s ig n a d v a n c e s o f b o th th e A P - D RG s a n d th e A ll P a tie n t
Re f in e d D RG s ( A P R- D RG s ) in p a tie n t c la s s if ic a tio n s ys te ms , a n d it a d d s a n
a mb u la to r y c o mp o n e n t. I R- D RG s w e r e d e s ig n e d n o t o n ly f o r u s e a s p a r t o f a f u n d in g
s ys te m, b u t a ls o f o r b u d g e tin g , o u tc o me s a n a lys is , b e n c h - ma r k in g , p e r f o r ma n c e
me a s u r e s , a n d u t i l i z a t i o n a s s e s s me n t . I n a d d i t i o n , I R - D R G s c a n c o mp a r e r e s o u r c e
u s a g e a c r o s s f a c i l i t i e s a n d r e g i o n s a n d su p p o r t l o c a l a n d n a t i o n a l h e a l t h s y s t e m
ma n a g e me n t.
I R- D RG h a s b e e n d e v e lo p e d to e f f ic ie n tly a n d e f f e c tiv e ly imp le me n t o th e r c o d in g
s ys te ms r e s u ltin g in n a tiv e v e r s io n s o f th e g r o u p e r f o r a w id e v a r ie ty o f d ia g n o s is
a n d p r o c e d u r e c o d in g s ys te ms . N o ma p p in g is u s e d a s ma p p in g in tr o d u c e s e r r o r in to
th e c la s s if ic a tio n p r o c e s s . I R- D RG s a r e d e s ig n e d to c o n f o r m to I CD - 1 0 , I CD - 9 - CM,
a n d I C D - 9 , a s w e l l a s t o a c c o mmo d a t e c o u n tr y - s p e c i f i c mo d i f i c a t i o n s a n d p r o c e d u r e
c o d in g s ys te ms .
Adjustments for Severity of Illness (SOI)
I R - D R G s i n c o r p o r a t e t h e c o n c e p t o f s e v e r i t y a d j u s t me n t t h r o u g h t h e u s e o f mu l t i p l e
le v e ls o f c o mp lic a tio n s a n d c o mo r b id c o n di t i o n s ( C C s ) a p p l i e d t o t h e b a s e p a t i e n t
g r o u p s . T h is me th o d o lo g y u s e s th e s e c o n d a r y d ia g n o s is in th e s a me e n c o u n te r , a s
w e ll a s c o mb in a tio n s o f s e co n d a r y d ia g n o s e s a n d b a s e D RG .
T h e c o n c e p t o f “ r e f i n e me n t ” i n D R G s ys t e ms i s n o t n e w . “ R e f i n e d ” D R G s w e r e
d e v e lo p e d to b e tte r e x p la in th e r e s o u r c e s r eq u ir e d to tr e a t p a tie n ts in a p a r tic u la r
D R G b y a d j u s t i n g t h e b a s e D R G t o i d e n t i fy t h o s e p a t i e n t s t h a t a r e s i c k e r ( mo r e
s e v e r e l y i l l ) , t h u s d if f e r e n t i n h e a l t h s t a t u s .
I n t h e a mb u l a t o r y c o mp o n e n t , t h e c o n c e p t o f a c c o mp a n y i n g min o r o r ma j o r c o mo r b i d i t i e s i s u s e d t o d e f i n e t h e b a s e p r o c e d u r a l D R G s . N o n - p r o c e d u r a l ( me d i c a l )
a mb u la to r y D RG s in c lu d e a n o p tio n a l c o mp le x ity le v e l w h ic h is b a s e d o n th e le n g th
o f th e me d ic a l e x a min a tio n o r c o n s u lta tio n , w h e n a v a i l a b l e i n t h e s p e c i f i c p r o c e d u r a l
classification.
R is k o f M o r t a lit y ( R O M )
I n a d d itio n to s u p p o r tin g e x p e c te d r e s o u r c e n e e d c a lc u la tio n s , c la s s if ic a tio n s ys te ms
a r e in c r e a s in g ly a s k e d to s u p p o r t o u tc o me e v a lu a tio n s . O n e imp o r ta n t o u tc o me is
mo r t a l i t y r a t e s . T h u s , D R G s y s t e ms n e e d t o s u p p o r t t h e c o mp u t a t i o n o f s e v e r i t y
a d j u s t e d e x p e c t e d mo r t a l i t y r a t e s s o t h a t t h e s e e x p e c t e d r a t e s c a n b e c o mp a r e d t o
e a c h h o s p i t a l ’ s a c t u a l r a t e s . I R - D R G s n o w i n c l u d e t h e a s s i g n me n t o f R i s k o f
M o r t a l i t y ( R O M ) , w h i c h i s t h e p r o b a b i l i t y o f d yi n g f o r a n a d mi t t e d p a t i e n t d u r i n g t h e
s a me e n c o u n t e r . R i s k o f M o r t a l i t y i s a n i mp o r t a n t o u t c o me p a r a me t e r o f q u a l i t y o f
i n p a t i e n t c a r e . T h e r e i s n o R O M as s i g n me n t f o r t h e a mb u l a t o r y s e c t o r .
I n c l u d in g s e v e r i t y a n d mo r t a l i t y a d j u s t me n ts i n i n p a t i e n t D R G s i s a v e r y i mp o r t a n t
c h a r a c t e r i s t i c t h a t e n h a n c e s t h e a b i l i t y t o u s e D R G s a s a c o mmu n ic a t i o n t o o l b e t w e e n
a d min is t r a t o r s a n d c l i n i c i a n s .
Details
A s a n e w g e n e r a tio n o f c la s s if ic a tio n s ys te m, th e I R- D RG s a r e d is tin g u is h e d b y th e
fact that they were designed specifically for—not adapted to suit—international
h e a lth c a r e . I R- D RG s w e r e n o t d e s ig n e d f o r u s e in a p a r tic u la r c o u n tr y. T h e f ir s t
v e r s io n o f th e I R- D RG g r o u p e r r e q u ir e d s e v e r a l la r g e d a ta s e ts to d e v e lo p a n d
s u b s e q u e n tly te s t in p a tie n t I R- D RG s , in c l u d in g a n in te r n a tio n a l d a ta b a s e c o n ta in in g
2 0 0 , 3 2 3 r e c o r d s f r o m th r e e c o u n tr ie s .
T h e s e c o n d g e n e r a tio n o f th e I R- D RG g r o u p e r h a s b e e n d e v e lo p e d a n d te s te d u s in g a
5 % s a mp le o f a ll a mb u la to r y a n d in p a tie n t CMS c la ims , in a d d itio n to a ll c la ims f r o m
t h e s t a t e o f M a r y l a n d , t h e o n l y a v a i l a b l e a ll- p a ye r e p is o d e s o f c a r e d a ta b a s e w ith
c h a r g e s a n d le n g th o f s ta y a v a ila b le in U n ite d S ta te s . O th e r la r g e d a ta b a s e s f r o m
S w i t z e r l a n d , B e l g i u m, a n d S i n g a p o r e w e r e u s e d t o v a l i d a t e t h e r e s u l t s .
I R - D R G s a r e b u i l t t o a t t r i b u t e i n p a t i e n t a n d /o r a mb u l a t o r y e n c o u n t e r s i n t o p r o c e d u r a l
D RG s o r me d ic a l D RG s . T h e c o n c e p t o f p r o c e d u r a lly- d r iv e n D RG s , w h e r e th e
r e le v a n t in te r v e n tio n d ir e c ts th e e n c o u n te r to th e a p p r o p r ia te p r o c e d u r a l D RG
a s s ig n me n t, s te e r s th e I R- D RG c la s s if ic a tio n s ys te m. E n c o u n te r s w ith o u t a
s ig n if ic a n t in te r v e n tio n a r e a s s ig n e d to med i c a l I R - D R G s . T h u s , t h e I R - D R G s a r e
“procedure driven.”
A s in o th e r D RG s ys te ms , a llo c a tio n in to o n e o f th e Ma j o r D ia g n o s tic Ca te g o r ie s
( M D C ) i s a c c o mp l i s h e d u s i n g t h e p r i n c i p a l d i a g n o s i s ( e x c e p t f o r M D C 2 3 w h i c h i s
a mb u la to r y o n ly) . I f th e r e a r e tw o o r mo r e r e le v a n t in te r v e n tio n s in a n e n c o u n te r ,
w h e th e r in p a tie n t o r a mb u la to r y, th e p r o c e d u r e c l a s s h i e r a r c h y d i r e c t s t h e M D C
a s s ig n me n t. T h is lo g ic s ig n if ic a n tly r e d u c e s th e n u mb e r o f D RG s f o r a p a r tic u la r
i n t e r v e n t i o n , a n d i t e l i mi n a te s t h e n e e d f o r “ u n r e l a t e d p r o c e d u r e ” D R G s . A r e c e n t
A u s tr a lia n s tu d y s h o w e d th e c lo s e r a lig n me n t o f th e I R- D RG v 2 . 0 to th e c lin ic a l
procedure, grouping encounters to 20% fewer IR-DRGs than the prevailing
c la s s if ic a tio n f o r th e 1 0 to p in p a tie n t p r o c e d u r e s . T h e f in d in g s s h o w e d “ mo r e
c o mp a c t a n d c l i n i c a l l y me a n in g f u l d e s c r ip tio n s f o r e le c tiv e s u r g e r y a n d p r o v e d to b e
b e t t e r p r e d i c t o r s o f r e s o u r c e r e q u ir e me n ts f o r t r e a t i n g t h e w a i t l i s t p a t i e n ts . ”
2
S p e c i f i c p r o c e d u r e s , s u c h a s c a t a r a c t a n d t o t a l j o i n t r e p l a c e me n t s , s h o w e d
c o r r e la tio n s w ith a s in g le I R- D RG , in c lu s iv e o f s e v e r ity le v e ls , o f g r e a te r th a n 9 0 % .
A s r e p o r t e d i n a r e c e n t B e l g i u m s t u d y u si n g a mb u l a t o r y d a t a , t h e c u r r e n t n a t i o n a l
c la s s if ic a tio n a s s ig n e d a p p r o x ima te ly 5 0 % mo r e g r o u p s th a n d id I R- D RG s . E v e n
w h e r e n o s e v e r ity a d j u s tme n t w a s d o n e , th e c u r r e n t Be lg ia n c la s s if ic a tio n s ys te m
r e q u i r e d 2 0 % mo r e D R G s f o r t h e s a me d a t a . 3
T h e r e a r e th r e e S e v e r ity o f I lln e s s s u b c la s s e s ( 1 , 2 , a n d 3 ) f o r a ll in p a tie n t D RG s
b a s e d o n th e p r e s e n c e a n d s e v e r ity o f c o mp lic a tio n s a n d c o mo r b id c o n d itio n s
( w ith o u t CC; w ith CC; a n d w ith Ma j o r CC) . T h e s e le v e ls d e n o te e x p e c te d r e s o u r c e
c o n s u mp tio n . T h e s e v e r ity le v e l s u b c las s a s s ig n me n t o f s e c o n d a r y d ia g n o s e s w a s
a c c o mp l i s h e d b y a n a l y z i n g t h e e f f e c t s o f e a c h p o s s i b l e s e c o n d a r y d i a g n o s i s a n d s o me
principal diagnoses on the resource usage and assigning one of three levels to each
d ia g n o s is . Re c o g n iz in g th a t c u r r e n tly mo s t in te r n a tio n a l d a ta s e ts c o n ta in a n a v e r a g e
o f l e s s t h a n t w o s e c o n d a r y d i a g n o s e s , t h e I R - D R G s d o n o t u s e mu l t i p l e C C s t o a s s i g n
th e s e v e r ity le v e l. T h is s ys te m a llo w s imp r o v e d in tr a - a n d c r o s s - c o u n tr y c o mp a r is o n s
a n d c a s e - mix a n a l y s i s .
I n a s i mi l a r v e i n , t h e r e a r e t h r e e R i s k o f M o r t a l i t y s u b c l a s s a s s i g n me n t s f o r e a c h
D R G . T h e s e w e r e a c c o mp l i s h e d b y a n a l y z in g t h e e f f e c t s o f e a c h p o s s i b l e s e c o n d a r y
d i a g n o s i s r e l a t i v e t o t h e p r i n c i p a l d i a g n o se s o n t h e p r o b a b i l i t y o f d e a t h a n d a s s i g n i n g
o n e o f t h r e e R O M l e v e l s t o e a c h d i ag n o s i s . R e c o g n i z i n g t h a t c u r r e n t l y mo s t
in te r n a tio n a l d a ta s e ts c o n ta in a n a v e r a g e o f le s s th a n tw o s e c o n d a r y d ia g n o s e s , th e
R O M s c o r e s d o n o t a l l o w mu l t i p l e C C s t o a f f e c t t h e R O M l e v e l .
Customization
A n in te r n a tio n a l in p a tie n t c la s s if ic a tio n s ys te m s h o u ld n o t o n ly e n c o mp a s s a r a n g e o f
c o d in g s ys te ms , it s h o u ld a ls o s imp lif y mo d if ic a tio n o f th e s ys te m f o r c o u n tr ys p e c i f i c r e q u i r e me n t s . I t i s a l s o i mp o r t a n t f o r t h e s y s t e m t o a c c o mmo d a t e
c u s to miz a tio n a s r e q u ir e d b y v a r io u s c o u n tr ie s w h ile ma in ta in in g a le v e l o f
c o n s is te n c y a c r o s s c o u n tr ie s . T h e in te g r ity o f th e b a s e D RG s th a t a r e th e f o u n d a tio n
o f t h e n e w s y s t e m p e r mi t s c o mp a r a b i l i t y a c r os s c o u n t r i e s . H o w e v e r , v a r i a t i o n s c a n b e
ma d e t o s u i t v a r i o u s i n t e r n a t i o n a l an d n a tio n a l p r o c e d u r e c o d in g c u s to ms a n d
standards.
Construction and validation
The IR-DRGs consist of 264 base inpatient DRGs, 110 procedural/intervention DRGs,
a n d 1 5 4 me d i c a l D R G s , e a c h w i t h t h r e e s u b cl a s s s e v e r i t y l e v e l s a n d t h r e e s u b c l a s s
r i s k o f mo r t a l i t y l e v e l s . T h e r e a r e 2 3 7 p ro c e d u r a l / i n t e r v e n t i o n a mb u l a t o r y I R - D R G s .
T h e r e a r e 5 1 b a s e n o n - in te r v e n tio n a l, o r me d ic a l a mb u la to r y, a n d 1 3 5 me d ic a l
a mb u la to r y D RG s , w h e n th e o p tio n a l a mb u la to r y i n t e n s i t y l a y e r i s u s e d . T h e r e a r e 1 4
e r r o r D RG s , w h ic h e x p a n d th e e x p la n a tio n th e o f n o n - a p p r o p r ia te g r o u p in g ( s u c h a s
in v a lid d ia g n o s is a n d p r o c e d u r e c o d e s ) , a ls o a v a ila b le . T h e to ta l o f 1 , 1 7 6 I R- D RG s
( b a s e D RG / S e v e r ity o f I lln e s s p a ir s ) a r e in c lu d e d in th e v e r s io n 2 . 2 c la s s if ic a tio n
s y s t e m.
A s n o te d a b o v e , I R- D RG s w e r e d e s ig n e d to b e c o mp a tib le w ith I CD - 9 - CM, I CD - 9 A N , a n d I CD - 1 0 , a s w e ll a s a v a r ie ty o f p r o c e d u r e c o d ig n s ys te ms . T h is r e s u lte d in a
s y s t e m t h a t a s s u r e s a g iv e n p a t i e n t w i l l f a l l i n t h e s a me I R - D R G r e g a r d l e s s o f t h e
c o d in g s ys te m u s e d . E a c h c o d in g - s ys te m- s p e c if ic v e r s io n o f I R- D RG s is a n a tiv e
g r o u p e r in w h ic h th e g r o u p e r lo g ic is e x p r e s s e d d ir e c tly in te r ms o f th e s p e c if ic
d ia g n o s is a n d p r o c e d u r e c o d in g s ys te m u s e d b y th e in d iv id u a l c o u n tr y. N o ma p p in g
b e tw e e n c o d in g s ys te ms is u s e d . U s in g n ativ e c o d e s to c o n s tr u c t D RG d e f in itio n s
p r o v id e s mo r e c o h e r e n t g r o u p in g s .
Independence from reimbursement mechanisms
A n e s s e n t i a l f e a t u r e o f a n y c l a s s i f i c a t i o n s ys t e m i s t h e i n d e p e n d e n c e o f t h e c l i n i c a l
c la s s if ic a tio n s c h e me a n d th e p a yme n t me c h a n is m, a llo w in g v a r io u s f in a n c ia l a n d
o p e r a tio n a l ta s k s . A D RG c la s s if ic a tio n mu s t s tr ik e a b a la n c e b e tw e e n th e n u mb e r o f
g r o u p s a n d th e d is c r imin a to r y p o w e r o f its s tr u c tu r e . I f a c la s s if ic a tio n b e c o me s mo r e
s p e c i f i c f o r r e i mb u r s e me n t i mp e r a t i v e s d r i v e n b y h e te r o g e n e o u s v e s te d in te r e s ts , it
ma y e x p a n d i n t o ma n y h u n d r e d s o f a d d i t i o n a l i n c o h e r e n t i n p a t i e n t g r o u p s . A
c l a s s i f i c a t i o n ma y i n c r e a s e i t s e x p l a n a t io n o f c o s ts a n d r e d u c tio n o f v a r ia n c e a s
c o mmo n l y me a s u r e d , b u t i t w i l l a l s o l o s e i t s s t r e n g t h a s a c o r e g r o u p i n g
me th o d o lo g y.
T h e n e e d f o r a s ys te ma tic , c o h e r e n t s e v e r ity le v e l a d j u s tme n t ma in ly
b a s e d o n c o - mo r b i d i t i e s a n d o t h er f a c t o r s i s w e l l r e c o g n i z e d .
Resource utilization measurements
E x p e c t e d r e s o u r c e u t i l i z a t i o n i n c r e a s e s mo n o to n i c a l l y a c r o s s t h e s e v e r i t y l e v e l s i n
e a c h I R - D R G . T h i s mo n o t o n i c p r o g r e s s i o n i s co n s i s t e n t a c r o s s a l l b a s e D R G s e v e r i t y
le v e ls f o r c o s ts / c h a r g e s ( r e s o u r c e w e ig h t) a n d le n g th o f s ta y ( L O S ) in th e U n ite d
States databases, and in the international databases for LOS in all base DRGs with a
s ig n if ic a n t n u mb e r o f c a s e s . F ig u r e 1 s h o w s a n e x a mp le o f th is mo n o to n ic
p r o g r e s s io n w ith a s a mp lin g o f D RG s in MD C 5 a n d 7 .
I R- D RG # - S O I
D e f in itio n
Average LOS
Re s o u r c e w e ig h t
05410 - 1
I M A c u te
Myocardial
Infarction
I M A c u te
Myocardial
Infarction w/CC
I M A c u te
Myocardial
I n f a r c t i o n w / MC C
2.33
0.688
4.56
0.970
7.20
1.568
05410 - 2
05410 - 3
07111 - 1
07111 - 2
07111 - 3
I P C o mp l e x B i l i a r y
Tract Procedures
I P C o mp l e x B i l i a r y
Tract Procedures
w/CC
I P C o mp l e x B i l i a r y
Tract Procedures
w/MCC
6.38
1.768
10.20
2.614
17.40
4.820
F ig u r e 2 s h o w s a n e x a mp le o f r e s o u r c e w e ig h ts f o r I R- D RG s in a s a mp le o f
a mb u la to r y p a tie n ts in MD C 0 6 .
I R- D RG #
D e f in itio n
Re s o u r c e w e ig h t
063140
Co mp le x U p p e r G a s tr o in te s tin a l
Endoscopy
N o n - Co mp le x U p p e r G a s tr o in e s tin a l
Endoscopy
O th e r G a s tr o in te r tin a l P r o c e d u r e s
0.948
063150
063160
0.693
0.641
Conclusion
Re v ie w in g th e e v o lu tio n a n d r e le v a n c e o f t h i s n e w I n t e r n a t i o n a l R e f i n e d - D R G ( I R D R G ) s y s t e m d e mo n s t r a t e s w h y e x i s t i n g a p p r o a c h e s t o c o mp a r i n g e p i s o d e s o f
in p a tie n t h o s p ita liz a tio n a n d a mb u la to r y p a tie n ts a r e n e ith e r c o n s is te n t n o r p r e d ic tiv e
of resource use. Existing approaches can be replaced by a system designed
s p e c i f i c a l l y f o r i n t e r n a t i o n a l u s e t h a t c a n a ls o p r o v id e c lin ic ia n s a n d h e a lth c a r e
ma n a g e r s w ith o b j e c tiv e a n d r e lia b le w a ys o f me a s u r in g th e s e v e r ity, r e s o u r c e
u t i l i z a t i o n o f h o s p i t a l i z e d a n d a mb u la t o r y p a t i e n ts w o r l d w i d e , a s w e l l a s e x p e c t e d
mo r t a l i t y r a t e s . T h e I R - D R G s a d d r e s s t h e c h a l l e n g e s o f t h e d iv e r s e i n t e r n a t i o n a l
d ia g n o s tic a n d p r o c e d u r a l c la s s if ic a tio n s ; th e y a r e id e a lly s u ite d f o r p e r f o r ma n c e a n d
q u a l i t y me a s u r e me n t a n d c o mp a r i s o n s .
References
(1) Mullin, R. Utilization Review. Based on Practitioner Profiles. Journal of Medical Systems. 1982; 7(5): 409-412.
(2) Deniza Masevska et al. Comparison of 3M International Refined (IR)-DRG and Australian Refined (AR)-DRG. Proceedings Patient Classification Systems International Annual Meeting. Slovenia, 2005 and Proceedings –WHO Family of International
Classifications Meeting. Tokyo, 2005
(2) Peter Fontaine et al. International-Refined (IR-DRG) versus 3M All Patients Refined DRG (APR-DRG) to describe and predict
costs of patients in 42 Belgium hospitals. - Proceedings - Patient Classification Systems International Annual Meeting . Slovenia,
2005 and Proceedings –WHO Family of International Classifications Meeting. Tokyo, 2005