NATIONAL DRG VALIDATION STUDY: FY 1985 

PEER REVIEW ORGANIZATION CODING ACCURACY 

RICH P. KUSSOW 

INSPECTOR GENERA 

12-9 AU 199

EXECUTIV SUMMARY


PURPOSE 

Th inpecton analyzs the accuracy of peer review organtion (PRO) cog 

diagnosis related groups (DRGs). 

BACKGROUND 

The"F 1985 National DRG Valdation Study rcced 7,050 dicharges strtied by 

hospita siz. The Ofce of Inpeor Genera (OIG) locted PRO rcabstrctons for 

23.9 percent of the saple. Th subsple accteJy represented the underlyg 

confounders. 

population by age, sex diagnosis related groups, and other probable 

FIDINGS 

The PROs cocc coed 78.1 percnt of reabstractons, a sigcatl lower 

proporton than the 81.8 percent accteJy pad by the Fis Intermedes. 

. A PRO that changed a DRG had a 90.5 percent chace of being wrong. 

. On average, the PROs upced their erroneous DRG reabstrctons, COD.poundig 

the fiancial effect of their lower cog acccy. These errors causd at least 

$172.9 mion in overpayments for Fisca Yea 1985. 

RECOMENA110NS 

The Health Care Financig Admitrtion (HCFA) should determe whether the 

proporton of PRO rcabstrcton errors ba deceaed 

The HCF A should determe whether the Super PRO alo fids th ditributon of 

chges to PRO coing. 

The HCFA should determne whether internal qualty controls of the PROs increae 

the acccy of their DRG reabstrctons. 

In the AprD 24 comments on a draf of th inpeon, the HCF A stated that it has 

taen a number of actons to improve the accacy of PRO coing. We agree that 

thes actions respond to the intent of these remmendations. The OIG is now 

collecg FY 1988 PRO cog data. Comparon of these independentl generated 

data sets wil meaure the progres achiev by the HCFA in improvg PRO cog 

accacy. 
. . . . . . . ........ ........... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...... 

.......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......................................... ...... ............. .... ............ ........... ........ ..... .......... ... ............... ......... ................ ........ ...... ....... ........ ....... ......... ...... ....... ........ ............. . . . . . . . . . . ............ ....... ....... .......... ..... . . . . . . . . ......

TABLE OF OONTENTS 

EXCU SUMY


TAB OF CO 

INODUcnON 

BACKGROUN. .


MEODOLOGY


FIINGS PRO 

PRO CODING ACCCY 

DRG EFCT 

RECO A110NS 

Apix PRO reew by hopita demography 

Appedi PRO revew by patient demogrphy. . . . . . . 

Apdi

Ap 

PRO cog acc by hospita demography 

F1 cog accracy by hospita demogrphy. . 

Ap PRO coing acacy by patient demogrphics 

AplX Statitica methocology 
INTRODUCTION


BACKGROUND


In 1972 Congress established the Professiona Stadads Revew Orgations (PSROs) 

as part of the Socal Securty Act. It charged the PSROs with ensurg that al servces 

deliered under Medicae and Medicad were medca neCss, conformed to 

appropriate professional stadards and were deliered effcientJ and ecnomicay. strcte restrcted revew 1982 however, Congress concluded that the PSRO 

inovtion necessa to lit esatig heath cae cots and protec agait por 

quality of cae. Therefore, under the Peer Revew Improvement Act Title 1, Subtitle C 

of the Tax Equity and Fisca Responsibilty Act of 1982, Public Law 97-24 Congress 

crted the Utition and Qualty Control Peer Revew Orgations (PROs). Ths 

legislation required the Seo/eta of the U.s. Deparent of Health and Hum 

Servces (DllS) to contract with either "physician-sponsored" or "physician-accss 

PROs. Each 2-year contract s "scpe of work" defied the actties to be performed by the PRO. 

Under the fit scope of work (19841986), the PROs recived performance-based 

objeces to counter potential negatie incenties po by the new prospee 

PPS, hospita could reduce cots by litig servces 

payment sytem (PPS). Under the 


and shortenig stays and increas payments by raing the number of adJsions- or


upcing the diagnosis related groups (DRGs). To control these trends, the PROs had 

thee admsion related goal: 

. Redce the number of ecessa admions.


. Veri that payment coes conformed to the diagnostic and procural inormation


in patient recrds. 

Revew caes of trfer or redmion ocg with 7 days of a prevous 

dihage. 

The fi scpe of work gave the PROs four method for cug utition or quaty 

deficiencies: Education, intensifed revew, denial of payment, and recmmendation 

a DHHS Ofce of Inspeor General (OIG) sacton for "substatial violations" in a 

substatial number of caes" or "gros and flgrt violation in a single ca. Each 

cotr al included fie quaty of cae objectes. 

Reduce unecss readmions. 

Umit prevntable complications.


. Reuce unnecssry surgery.

. Loer the rik of mortalty.


. Lit avoidable postoperati complications. 

. To att these goal and objeces, the PROs recived guideli for exactg data 

about the physician and provders in their area In the fit scpe of work, these


included:


Five percent radom saple of admisions 

Pacemaker cases 

Trafers from PPS hospita to other hospita except swg bed


Readmisions with 7 days of dichage


. DRG reabstracton of DRG 46 and DRG 462 bils


Statitical outliers


Under the PPS, hospita recive a pr-etablihcd payment for each dicharge, based 

upn the DRG to which the dicharge groups. The PPS clasifed dihages into 

clca coherent groups tht use siar amounts of hospita resource baed on 

vables such as diis; evuation and treatment procures; aDd patient age, sex, 

and diharge statu. Each of the 473 DRGs had an asted relatie weight, which 

represented the average cot for hospita cae provded to patients with dignoses 

cot of al patients. The hospita recived gruping to that DRG as a proporton of the 

th payment independent of the actl length of hospitation or cot of treatment for 

the indivdual patient. The hospita retaed any surlus from patients coumg less 

th the exed amount of resurces, and absorbe a los for patients consumg 

more. 

Optiona, the PROs reabstrcted PPS bil to check the acccy of DRG payments 

to hospitals. The PRO revewers compard dignosc and procur inormation from 

the medca recrd to the nartie dignoses and proures attesed to the attendig 

phyic and the conversion of natie inormation to ICD9- (International 

Cascation of Die) coes. A regitered recrds admitrtor (R) or an 

acedte recrds tehncian (ART) genera superv the rcbstrcton. 

Disge 16.547.674

Dmg PRO 576. their fit scope of work, the PROs claed 

(Pernt) (33. have reabstrcted . 33.7 pcrcent of PPS bil. Among 

radomJ seleced disharges, they found 4.8 pcrcent to So' PP Mong Co.. Repor1

9.2 m error. error rate contrt WI on pp Mooc Ac. Feb. '2.1887 

8 pcrcent 
 Tab 1. PR rf . ielS&Rthfi percent reported by the SupcrPRO and the 20.

repoed by the "F 198 National DRG VaHdatioD 8C 

Study Fin Report. 
(%) 

Sources both inide and outside of the Rev caegor DRG error 

DHHS studied PRO performance under 975,280 47, (4. the fit scpe of work. In the second Ra sae 

scpe of work (19861988), the Health Intensie 319, 18,721 (5. 

DRG 160, 18, (11. 

Cae Financig Admitration (HCFA) Otr 121,505 141, (3.


adopted many of their fidings to


strengthen PRO revew. These changes Tot 576, 22, (4.


included exanding revew from Tab 2: DR vainre fo th fi PR 


redmion with 7 days of a prior at 

diharge to readmision with 15 days 

of a prevous discharge. The PROs also sapled dihages for evdence of prematue 

dihage or trnsfer. In addition, they reewed hospitas with unexlaied statitical 

outlers in mortlity rates and utition pattern. The PROs recived a stadad set of 

quaty sceens to apply in aU caes seleced for review. They alo revewed short. stays 

in the hospital and developed and implemented communty outreach progr. Al 

rerds seleced for reyew were subjeced to DRG vadation, and the PRO bad to 

have at leat one credentialed medica recrds profesional on its sta. 

the HCFA drew on exensive analis of PRO 

In devloping the thrd scope of work,
 scpe of work. It alo incorprated changes mandated in 

actties under the second 


the followg public laws passe since the implementation of the send scpe of work: 

Public Law 99-272, the Consolidated Omnibus Budget Recnciation Act of 1985 

(COBRA); Public Law 99-509, the Ombus Budget Recnciation Act of 198 (OBRA 

86); and OBRA 87. 

The thd scpc of work remaed conant with the send, but added seera 

signcat amendments. To make PRO actties more consistent acros contrctors 

the HCF A develope a baic quaty intervntion pla under which the PROs follow a 

stdadi procss for categorig quty prblems notig provders and 

intitutig interventions. Al, revew of hospita readmions exded to patients 

redmtted with 31 days. Oter new requiements include: 

Perform a signcat number of on-site reew in at leat 20 pcrcent of rura 

hopitals. 

Revew the reonableness and medca necity of iniv procures. 

Conduct a revew of ambulatory surgery procdures. 

Conduct intensifed revew of thos physicians provders, and DRGs found to 

exbit a pattern of substandard cae. 
.. ., 

. Revew post-hospital intervenig cae for which Medicae payment could be made, 

that is deliered between two hospita readnions where the send admion 

withi 31 days of discharge from the fit admision. 

meaure PRO actties, the HCFA requied month and The HCFA evluated PRO performance in II thee ways. To Cycl Pernt 

quarerJy report sumarg admiion revew, DRG


vadations, pre-admission revew, and other requied revew 1 12/849/8 9.


data. To evuate PROs more broadJy, the HCFA created the 2 6/852/86 9. 

(pROMP2). 3 11/857/86 11. 

PRO Monitorig Protocl Trackig SfStem 


The PROMP-2 surveyed PRO performce bianuall in 6 6/87-388 9.
 such area as community outreach, gement, internal 

contrls sactons, and medica revew data Final, the Table 3: SuperPRO 

HCFA contrcted with Systemetrcs InC., al know as the 

4 PRO SupcrPRO, for a bianual review of approxateJy 40 ca from each of the 

area. For each of the caes, SuperPRO repeted the PRO revew proc using both 

the generic quality sceens and each PRO's ow crteri It compaed it reults to 

thos of the PRO. The SuperPRO then submitted dr and fi report of its fidigs 

to the HCF A. The PROs and HCFA follow-up the Super PRO's fidigs in an effort to 

improve PRO performance. 

Th inpeon exes one aspe of the PRO revew proc: DRG vadation. The 

HCFA relies on the PRO vadation proc to ensure hospita cog acccy. The 

hospita must coe thir diharges accateJy for the PPS to reimbur them faJy and 

for cot containent. Under PPS, the hospita forwd each bil' ICD9- dignosis 

and procure coes dicc to a stte Fis Intermed (P). .The PI groups the 

ICD9- coes to determe the correc DRG, reimburs the hospita and sends ths 

inormtion to the HCFA. The PROs then revew a radom saple of these 

asignents (plus certin spc DRGs) for cog acccy. 

MEOGY 

The Nationa DRG Valdation Study employed a strtied two-stage saple design 

ba on hospitals and discharges. In the fit stage, the OIG us siple radom 

saplig without replacement to selec 80 hospita from each of thee be siz stta: 

Hosta with les than 100 be 100299 be and 30+ be. Tbe design excluded 

spty intitutions (e.g., peiatrc, rehabiltation, and pschiatrc hospita), facities in 

States not using prospecive payment at the tie (i.e., New York, New Jers, 

Machustts and Maryland), and hospita not contn"butig data to the c:cuation of 

the inti relatie weights asigned to diagnosis-related groups. One saple hospital 

IUs. At 0f of Gt Se A4m NtI Sq 12, 198; 53 (116): J523. 

HtIf. JJ PRO 

hI Rq. 

(%) 

termated its Medicae eligibilty between the study pcriod and actal collecton of 

medica records, leavig a fit-stage sap1e with 239 from a popu1ation of 4,913 acute 

cae hospita. 

In the send stage, a sytemic Be sie c:100 1-2 30+ Totl 

radom sap1e se1ected up to 30 

Medicae patients (including HosDitals 

2.53 1,60 774 4,913 

pcrsns trferred to other poplaion 79 80 80 23 

hospita and those who died) Sam 

from each of the 239 hospital for is 

Pop':io (00,00) 5 3.1 3.6 8. 

If the hospita dicharged fewer Sa hopils (00) the fit hal of Fisca Yea 1985. 

18.2 59.5 144.7 22. 

th 30 patients durg th Sam 2.276 2.38 2.38 7, 

avable dicharges Saming fr 

period al 


were se1eced. The OIG -then Tab 4: Sa fr (12.5) (4.0) (1.6) (3. 

copy of each of the 7,076 medca recrds selected. With caefu1 

reueste a cop1ete 


follow-up and se1ece use of subpona the OIG ultiteJy obtaed 7,050 char 

(99.6 percent). The sap1e accateJy represented the popultion of al Medcae


benecies dihaged durg Fis Yea 1985.


The OIG contrcted with the Heath Data Intitute of Legton, MA to reabstrct the 

DRGs on a blided basis. Accited Recrd Technci enmined each cha and 

convrt the supportble diagnoss and procures into ICD9-. coes. A 

pred spty

Regitered Recrd Adtrtor superved the cog te and contrctor physician 

advce about spc questions. If the rebstrcted DRG diered 

from the DRG paid, a physician evuate the char on a blided bais. A physician 

dicut categoritions. Five percent of the entie saple radoml 

pael decded


underwnt a sed, blided recg by a dierent ART to meaur the acccy 

Th quty control pr reed no signcat the reabstrcton method010gy.
 diepaes in the rebstracton pro (agrent 0.95, kappa 0.856, Z 2.12). 

The OIG subsuentl asked the PROs Percent 

bd rea trcted the roar


and if so, the resu1ts of the rccg. The


PROs reported reabstrctg 1,728 of the 20 ..


050 sap1e disharges, 23.9 pcrcent


when weighted by disharges. Smaler


hospita had signcady higher rates of 

PRO rebstracton (Ch-squae 28.5, 2 df, c100 100-299 300.. 

Pc: 0.00 1). AppropriateJy, the "F 198 

Bed size


National DRG Validation Study Fin by tht smaller Fvn 1: PR 

Report" prevousJy noted 


intutions have higher rates of bilg errors.

FINDINGS 

PRO 

The PROs disproportonateJy reabstrcted char from rual (Mantel-Haensl 56. , 1 

df P OOl) and nonteachig hospita (Mantel-Haenszel '?. , 1 df P OOI). As 

reported by the "F 1985 National DRG Valdation Study: Final ReporttI hospita 

diproportonate rates of bilg errors when 

exhibiting these characteristics suffered 

controllg for bed size. The PRO selecon of dichages appropriateJy concentrted 

(Appendi 1). on intitutions with a high yield of reabstracton errors. 

Patient demogrphic charcteritics for 0--'" 

the 1,728 records reabstracted by PROs m Iot-­

did not signcatly dier ftom the 5,322 

remaig recrds in average lengt of 

sty, mortity rate, or sex distnDution. 

However, the former subsample 

averaged slightly older than the latter


group of patients (t-test 4.5, 1727 df,


025). The PRO saple therefore Fi 2: PR re by pa 

Medcae broadJy represented the al 


cas. (Appendix 2). 

PRO CODING ACCUCY 

When weghted by dicharges, the PROs Percent 

t: FI
 atted 78.1 pcrcent accuracy in their 100 

E PRO
 coing reabstractons. Their acccy 

improved signcatJy in larger hospita 

(Ch-squae 11.2 2 df, P=O.OO).


Controllg for hospital siz, PRO


rebstrcton acccy signcatl


deteriorated in rul (Mantel-Haensl . S eO size


14.7, 1 df P OOl) and for-profit 


hospita (Mantel-Haenszel 3.8, 1 df fi 3: PR 

P-=0.05), but not in nonteachig intitutions. The PROs increaed their effciency by 

greater sureilance of ru hospita but then deceaed their effeceness -wth lower 

cog accacy in rural hospita. (Appendix 3). 

accteJy than the PROs intended to overse them. 

InterestigJy, hospitals coe more 


The "F 1985 National DRG Valdation Study: Final Report" found that the 


acctely paid 81.4 percent of bils, weigted by dicharges. Ths proporton

signcantly exceded the PROs' 78.1 percent coing accacy (Ch-squae 25.8, 1 df, 

OOl). Among the 1,728 discharges reabstrcted by the PROs, the PI accately 

pad 81.8 percent, a 1.05 rate ratio. Th fidig applied acros al hC?pita sizs and 

(Appendi 4). The subsamples of dichages rcabstracted 

demographic characteritics. 


correcJy and incorrectJy by the PROs did not dier signcatl in patient

demogrphics. (Appendix 5).

PRO OUTCOtlE 

( DRGJ 

Agree 1282 True posi ti ves ( eorect) Ac:cura te


1. 3BB 

Disagree 

(Incorrect) 106 False negatives 

Agree 299 Type 1 false pos1 ti ves 1 . 728 ( Incorrect) 

Inaccurate Disagree 

340 27 Type 2 false positives ( Incorrect) 

Disagree 14 True nega ti ves ( eorect)

Fi 4: PRO co 

A PRO' s reabstcton of the PI's payment has fie poible outcomes. If the PI made 

the accrate payment, the PRO ca either agree (tre positie) or digree (fale 

negatie). If the PI paid inacctely, the PRO ca agree (ty 1 fae positie) or 

digree. The latter digreement may cause the PRO to reabstract the diharge to 

either the correc DRG (tre negatie) or to a dierent, incorrec DRG (ty 2 fae 

potie). (Figue 4). 

Of th saple s 1,388 bil accteJy 

reimbur by the Fl the PRO 

correc agreed in 1,22 caes; a 

seitty of 92.3 percent. Howr, 

the 34 bil inaccrateJy pad by the Fl 

the PRO correctJy disagreed and 

substituted the right DRG in onl 14


ca a 4.1 pcrcent speifcity.


DRG fisl Intermiarv
 Ace lne Tot 

129 PRO ( Co 1282 

DRG ( Inec 106 

Total 138 340 1728 

Sensitiv - 923% Spe -= 4.1 % 

T8b 5: PRO co 

For ths subsample as a whole, PI 

reimburment alone would have ben correc in 80.3 pcrcent (1388/1,72) of 

diharges. The PRO revew deceaed tota correc payments to 75.0 pcrcent 

07 rate ratio. Under Bayesian anaJyis, if the PRO maes no DRG 

(l,/1,728), a 1.

changes, it has 81.1 percent (1,282/1,581) chance of being correct. However, if the 

PRO elect to change the DRG reimbured, it has a 9.5 percent (14/147) chance of 

being correct. The PROs would therefore make a higher proporton of correct 

deciions by not checkig the FI's payment at al. Th strategy minimi7.e both review

costs and errors. When the nres. PROs do make DRG changes, they are wrong 10 out of

Relative weiaht Percent increase 

Outcomes Number FI Correct PRO (decease)

True poitive 1282 1157 1157 1157 

False negative 106 1140 1140 0707 (4. 

Type 1 false poitive 299 0755 947 0755 14. 

Type 2 fal poitive 1.20 0757 0498 (2.5) 

True negative 2998 0247 0247 (26. Total 1728 1.1118 0845 1042 

Tab 6: Ree we by PRO 

DRG EFFECT 

Not only do the PROs have worse coding accuracy than the FIs, they then compound 

the fiancial effect of their mitakes by upcoding. Overall, the relative weights selected 

by the PROs, whether for correct or incorrect DRGs, exceed by an average of 1.9 

percent either the correct relative weights or the relative weights paid by the PI. Type 

1 fale positives pricipally cause the acceleration in overpayment. However, other 

outcomes alo selectively contnbute to it. 

Of the 106 bils that the FI accurately Relative weicht

reimbured and with which the PRO then DRG paid No. Paid PRO 

incorrecty diagreed, 27.4 percent grouped


to only five DRGs. On average for these Pneumonia 9 0914 783


high frequency DRGs, the PRO incorrectly 127 Heart failure4 0300 4150


Arythmia 4 9200 9314 

assigned their bil to higher relative Angina 7470 7305 

weights than the PI accurately paid. 182 Esophagitis 7 6121 9646 

Although thi trend did not continue for


less frequent DRGs, selective Subtotal 29 0.8842 0.9255 Other 77 1.1868 1. 1254 improvement in PRO coding accuracy of Total 106 1.1140 1.0707 

false negatives could reverse the net overreimbursement due to PRO coding errors. Table 7: Acrae pame in ch

th PRO (f negates) 

Similarly, 29.8 percent of the 299 bils inaccurately paid by the FI and with which the 

PRO incorrectly agreed group to seven DRGs. For each of these DRGs, the PRO also 

confrmed an average reimbursement higher than the correct DRG. Less frequent 

DRGs and the subsample as a whole demonstrated the same upcoding. Overall, these 
. 

J=elative weicht

Among 27 inaccrate bils Number Paid Coec II DRG 

that the PROs changed to 14 Ceebrovasla acnt 783


diferent, incorrect DRGs 0177
 87 Respiraor failure 

. 481 857 pcrcent group to six

DRGs For these DRGs 88 Chronic obruive 

pulmo dis 

the PRO selections alo 89 Pnemoia . 18 1.0914 0.9827 

overpay the hospitals to a 127 Hea failure 12 1.03 0.954 132AtheOSis 11 0.907 0. 

greater extent than the Fls. .


Overal ty 2 false 182 Esgitis 14 0.6121 0.8115 

the Subotal 89 1.0704 089 poities dow coe Otr 210 1.0776 0:96

FI' relatie weight by 2. Total 29 1.0755 0.947 

percnt. The small 

Dumber of tye 2 false Tab 8: lne pa wi wh th PR 

poities and
tre negatives ages (t fa po) lits their net eff ct On PRO upcing of FI inacccies. 

The PROs' cog errors elative wei 

cot Medicae a mimum DRG Number PRO Coect 

of $172.9 mion in Fiscal 

14 Cebrov 690 

Yea 1985 and potentially 88 Ch obe 708 

lager sums in subsquent pu diase 

yea Prosive Part A 1547 89 Pneumia 739 

payments totaed $27 29 Metic 6121 697 bilon in Fis Year 1985. 32 Uri trct Inecio


The PROs reabstracted 46 Unred prure 7016


33.1 pcrcent of diharges, Subotal Otr 13 0.93 0.859 

skewed towds high Tot 14 1.157 1.298 

%1 1.0498 1.0757 reimbursment DRGs. 

The PROs therefore made Tab 9: lne pa wi wh th PR 


their 1.9 pcrcent DR (t 2 fa po) to a .


dfer 

ovyments on at least


$9.1 bilon of coing revews.

RECOMMENDATIONS


. The HCFA should determe whether the proporto of PRO reabstrcton errors 

has decreaed.


The HCF A shou1d determe whether the SupcrPRO alo fids th ditribution of


changes to PRO coding.


. Tbe HCFA should deteime wheter internal quaty controls of the PROs increase 

the accuracy of their DRG reabstrctons. 

In the Apri 24 comments on a dr of th inpeon, the HCFA stated that it has 

taen a number of actions to improve the acccy of PRO coing. We agree that 

these actons respond to tle intent of these recmmendations. The OIG is now 

collectg FY 1988 PRO COing data. Comparon of these independently generated 

data sets wi measure the progres achieved by the HCFA in improvg PRO cog 

accacy. 
(%) 

\ppenclX 1: PRO rew by hopi 

Number ed size Discharge weigted 

(per nt PRO c: 100 100299 300+ Tota average 

reabstractions 1


Urban 119 (26. 323 (19. 471 (21. 940 (21. 

Rural 528 (29. 22 (31. 65 (45. 788 (37. 

Teachig 19 (31. 94 (20. 233 (17. (21. 

Nonteachig 628 (28. 451 (23. 303 (28. 1382 (26.4) 

Profit 50 (23. 99 (23. 14 (23. 163 (23. 

Nonprofit 597 (28. 44 (22. 522 (224) 1565 (23. 

Total 647 (28. 545 (22. 536 (225) 1728 (23. 

Apnd PRO re by pant delOra 

ed size Wei hted rcenta 

c: 100 100299 30+ Saple Disharge Hospita 

Age PRO revew 75. 74. 72. 74. 73. 74. 

(yea) No revew 75.5 73. 71. 73.3 72.8 74. 

Sex PRO revew 47. 45. 47. 46. 46. 46. 

(% male) No revew 41. 45. 48. 45.2 46. 44. 

l.S PRO reew 7.2 8.7 7.3


(days) No reew 7.5 7.2 7.5


Mortity PRO revew 7.3 

No revew 
(y) 

.ppenclX 3: 
PRO cong acccy by ho dera

iihted rcenta 

l1umber ed size 

100299 300+ Tota Saple Discharge Hospita Percent correct) c: 100 

(77. (78. (75. urban 87 (73. 245 (75. 398 (79. 730 

(71. 

Rural 370 (70. 172 (77.5) 24 (63. 566 (71. (72. 

271 (78. (79. (67. reachig 11 (57. 72 (76.6) . 188 (80. (75.2) (73. Nonteachig 446 (71. 345 (76.5) 234 (77.2) 1025 (74. 

6 (42. 112 (68. (67. (68. 

Profit 38 (76. 68 (68. (77. (74.

Nonprofit 419 (70. 349 (78. 416 (79.7) 1184 (75. 

Total 457 (70. 417 (76. 422 (78.7) 1296 (75. (78. (73. 

Ap 4: R cong accra by ho dera ted 

Number ed size Wei rcenta 

(percent accte) c: 100 100299 300+ Tota Saple Dicharge Hospita 

Urb 94 (79. 26 (83. 399 (84. 761 (82.2) (83.0) . (81. 

Rur 391 (74. 185 (S3. 51 (78. 627 (78. (79. (77. 

(81.2) (75.

Teachig 13 (68. 77 (SI. 200 (85. 290 (7S. (79.
 Nontechi 472 (75. 376 (83. 250 (82) 1098 (SO. (81.5)


(74. (72.6) (76.4) 9 (64.
 Profit 39 (78. 79 (79. 127 

(79. 

Nonprofit 44 (74. 374 183. 441 (84.5) 1261 (81.0) (82.4) 

Tot 48 (75. 453 (83. 450 (84. 1388 (SO. (81. (79. 

Ap 5: PRO cog accy by pa 

Correc Incorrect 

Age 74. 74.


Sex (% mae) 46. 46.


LOS (days)


MortJity (%)

ApIX 6: Stca 

1. M dWi 

2. P dWi 

3. SE = (dW?SE?)l!2 

4. SEp = (dWi2pi(Pil)/Ni)l!2 

Where: 

d = sumation


p -= the popultion mean, 

P p = the proporton of a populatio with some characteritic, 

SEt =. the stadad error of the mean 

SEp = the stadard error of the proporton,


= the stta weights,


= the stta means


= the strta proportons,


s& -= the stta stdard errors. 

When cacutig statitics for meaurg relationships in cros-tabulations BOTEC used the 

followg procure: "Firt, we caculated tables sepateJy for each. strtum. We then 

weighted each entr of each table by its sttu weight, sumed the entres to get an

th table by the sum of the sttu weights. The 

overaD table, and divded each entr in 

wa used to cacuate the stengt of saple relationships and the 

resultig weighted table


sttitica sicace of such relationships. 

One fuer complication ocrs frequentl in BOTEC's sttitica analis of Nationa DRG 

"Smeties the foc of our anis is upon hospita at other 

Valdation Study data. 


ties it is upon indivdual Medicae cas. In the former ca the stta weigts we use


are the iners stta saplig rates for hospitals i.e., the ratio of the tota number of 

hospita in each strtum to the number of hospita which National DRG Valdation Study 

sapled from tht sttum. In the latter cae the strta weights used are the inverse 

tota estiated number of Medicare saplig rates for Medicare caes, i.e., the ratio of the Valdation ca in each strtum to the number of Medcare caes which National DRG 

Study sapled frm the strtum.