what are internists looking for?
TRANSCRIPT
JGIM
LETTERS TO THE EDITOR
Comorbidity and Length of Stay: Statistically Significant?
To the Editor:--Matsni et al.1 repor t t h a t comorbid i ty as mea-
su red by the Cha r l son index was associated with a statist ically
s igni f icant inc rease in l eng th of s t ay for p a t i e n t s hospi ta l ized wi th
ches t pain. The pa r t i a l R 2 for comorbid i ty in the i r mu l t iva r i a t e
model s u g g e s t s t h a t abou t 0.3% of the total va r i a t ion in length of
s t ay was i ndependen t ly exp la ined by comorbidi ty. Moreover, of
the va r i a t ion explained, comorbid i ty a c c o u n t e d for a b o u t 0.7%
( .0034/ .5103 , from Table 4). Adjus t ing for mul t ip l e c o m p a r i s o n s
(at l eas t 18 in the mul t iva r i a t e analysis) , I would g u e s s t h a t the
overall impor t ance of comorbid i ty m a y not be s ta t i s t i ca l ly signifi-
cant .
In fact, w h a t is s u r p r i s i n g a b o u t these r e s u l t s is t h a t comor-
b idi ty i ndependen t ly exp la ined s u c h a sma l l a m o u n t of the var ia-
t ion in length of s tay. It s e e m s t h a t p h y s i c i a n s genera l ly ignored
compl ica t ing nonca rd i ac medica l factors in t r ea t ing pa t i en t s with
ches t pain. Whe the r th is is good or bad is unc lea r . All in all, the
d a t a sugges t tha t , for ches t pa in hosp i t a l i za t ions , col lect ing infor-
ma t ion on comorbid i ty provides very li t t le usefu l in format ion for
hea l t h services r e s ea r che r s or r esource u t i l iza t ion m a n a g e r s . - -
DAI~II~L J . CHlgR, MD, Palo Alto VA Health Care Sys tem, Calif.
REFERENCES
1. Matsui K, Goldman L, Johnson P, Kuntz K, Cook E, Lee T. Comor-
bidity as a correlate of length of stay for hospitalized patients with acute chest pain. J Gen Intern Med. 1996; 11:262-8.
In reply:--Dr. Cher h a s appa ren t l y m i s r ead Table 4 and ci ted
the par t i a l R 2 for "Rales on in i t ia l e x a m i n a t i o n " - - t h e l ine below
the informat ion on Cha r l son index scores. Nevertheless , his ob-
se rva t ion t h a t comorbid i ty score s eems to expla in only a smal l
pe rcen tage of the var iab i l i ty in l eng th of s t ay in th i s popu la t ion is
wor th address ing , s ince the correct par t i a l R 2 was .005. In the
overall popu la t ion of p a t i e n t s wi th ches t pa in , the majo r "drivers"
of l eng th of s t ay were, not surpr i s ing ly , the d i agnos i s of acu t e my-
ocardia l infarc t ion (R 2 - . 12), pe r formance of coronary a r te ry by
p a s s graft su rge ry (R 2 - . 19), and the occur rence of compl ica t ions
s u c h as congest ive h e a r t fai lure (R 2 - .05) and r ecu r ren t i s chemic
pa in (R 2 = .06}. Among u n c o m p l i c a t e d pa t ien t s , however, comor-
bidi ty score accoun ted for a b o u t as m u c h of the var iab i l i ty in
l eng th of s t ay as a pr ior h i s to ry of acu t e myocard ia l infarct ion,
and a C h a r l s o n score of four or more was a s soc i a t ed wi th an ad-
j u s t e d inc rease in l eng th of s t ay of 41% compared to pa t i en t s wi th
scores of 0 to 1. For example , th i s inc rease in comorbid i ty score
would be a s soc i a t ed wi th an inc rease in l eng th of s t ay of 1.8 days
compared to the m e a n leng th of s t ay of 4.5 days seen a m o n g pa
t i en t s wi th Cha r l son scores of 0 or 1. We would note t h a t our d a t a
a lso d e m o n s t r a t e a c lear "dose-response" effect be tween comor-
b idi ty score and leng th of s tay. Therefore, we conc lude tha t co-
morbid i ty as m e a s u r e d wi th Cha r l son index can improve analy-
ses of l eng th of s t ay for p a t i e n t s wi th acu t e ches t pain. Whe the r
o ther indices of comorbid cond i t ions migh t provide even g rea te r
in format ion r e m a i n s to be d e t e r m i n e d . - - T H o M ~ H. LEE, MID.
Partners Communi ty HealthCare, Inc., Boston, Mass.
500
What are Internists Looking For?
To the Editor;---Clinical pract ice gu ide l ines a re proliferat ing.
Al though some p h y s i c i a n s worry abou t the i r impac t on cl inical
a u t o n o m y and sa t i s fac t ion wi th cl inical practice, m o s t phys i c i ans
apprec ia te the i r po ten t ia l benefit . Only recent ly have inves t iga-
tors b e g u n to ana lyze w h a t specific f ea tu res m a k e for effective
prac t ice guidel ines . In the i r article, Hayward et al. n icely identify
some of those fea tures s u c h as the impor t ance of concise recom-
menda t ions , the inc lus ion of a synops i s of s u p p o r t i n g evidence
and quan t i f i ca t ion of benefit.1
One a rea t h a t was not a d d r e s s e d in the i r s t u d y is the impor-
t ance of a d e q u a t e d i s s e m i n a t i o n of informat ion. Pract ice guide-
l ines can be of g rea t benefi t to c l in ic ians . They also imply a s t an -
dard of care. However, gu ide l ines are not helpful if p h y s i c i a n s do
not know of the i r exis tence. Frequent ly , th is is due to n u m e r o u s
socie t ies p u b l i s h i n g gu ide l ines in the i r own subspec i a l t y jour -
na l s , m a n y or m o s t of which genera l i n t e rn i s t s do not read on a
r egu la r bas i s . A Medline s ea r ch of prac t ice gu ide l ines for the yea r
1995 yielded 38 a r t ic les of po ten t ia l impor t ance to genera l inter-
n is ts . These 38 ar t ic les were d i s t r ibu ted a m o n g th i r ty-one differ-
en t journa l s . Thir ty th ree (87%) of the pract ice gu ide l ines were
p u b l i s h e d in subspec i a l t y jou rna l s . The ar t ic les cover i m p o r t a n t
i s s u e s s u c h as the m a n a g e m e n t of d iabetes , 2 os teoar thr i t i s , 3 and
divert icul i t is . 4 To a d d r e s s th i s problem, 1 would like to sugges t
t h a t a wide ly-c i rcu la ted j o u r n a l for genera l in te rn i s t s , s u c h as
JGIM, regular ly pub l i sh an a n n o t a t e d b ib l iography of c l inical
prac t ice guidel ines . As more prac t ice gu ide l ines are pub l i shed
and the i r importayme grows, we c a n n o t say t h a t ignorance is
b l i s s . - - B ~ M. /kBOFF, MD, Medical Center o f Delaware,
Newark .
REFERENCES
1. Hayward RS, Wilson MC, Tunis SR, Guyatt GH, Moore K, Bass EB. Practice guidelines, What are internists looking for? J Gen In-
tern Med. 1996:11 : 176-8. 2. American Diabetes Association. Clinical practice recommenda-
tions 1995. Diabetes Care. 1995;18(Suppl}: 1-96. 3. Hochberg MC, Altman RD. Brandt KD, et al. Guidelines for the
medical management of osteoarthritis. Part 1. Osteoarthritis of the
hip. Arthritis Rheum. 1995:38:1535-40. 4. Roberts P. Abel M, Rosen L. et al. Practice parameters for sigmoid
diverticulitis. The Standards Task Force Amei-ican Society of Co-
lon and Rectal Surgeons. Dis Colon Rectum. 1995;38(2]: 125-32.
In reply:--The a u t h o r s agree ent i re ly wi th Dr. AbofFs obser-
va t ion t h a t genera l i n t e rn i s t s could benefi t from a widely avail-
able a n n o t a t e d b ib l iography of cl inical p rac t ice guidel ines . In-
deed, the Guidel ine Appra i sa l Project, wh ich conduc ted the
Pract ice Guide l ines survey upon wh ich our ar t ic le is based, h a s
more recent ly in i t ia ted an effort to bu i ld an inventory of evidence-
b a s e d prac t ice gu ide l ines toge ther wi th s t r u c t u r e d a b s t r a c t s of as
m a n y as possible . This eflbrt is s u p p o r t e d by a g r a n t from the Na-
t ional Library of Medicine and is now get t ing underway. Informa-
tion abou t the project and a rap id ly growing inventory can be
found on In te rne t a t h t t p : / / h i r u . m c m a s t e r . c a / C P G . - - R O B E R T
I - I n Y w ~ , MD, McMaster University, Hamilton. Ontario, Canada.