BOOKS OF RtfiDIfGS - PAHO/WHO
BOOKS OF RtfiDIfGS - PAHO/WHO
BOOKS OF RtfiDIfGS - PAHO/WHO
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?Vol. XVIII. No. 2. Sttilluleareiltte<br />
- 49 -<br />
strongly related to age and Lage was<br />
selected ats a partitioniiiig variable, thenl<br />
secon(idary diagnosis would not aippear<br />
powerful in subsequent clustering.<br />
Groups were then generated bas i on<br />
the most appropriate variable, that is, the<br />
one that .et as nainy of the criteria<br />
specified above as possible. In particular, it<br />
1) exhibited a significant reduction in variance<br />
relative to iiost ot the other variablles,<br />
2) created a manageablie ni tilher of>groil>ps<br />
based on the relatively smaill iinlmer ol<br />
values of the independeit variable, and 3)<br />
createtl groups whiose ueaiits were signilicantly<br />
dlitierent. Also. grotups Ibruied were<br />
homogeneoxns troni a clinical perspective.<br />
Once each Mlajor Diagnostic Category<br />
was initially pairtitioled inito suilgrotips<br />
based on the valiues of an independent varíable,<br />
a decision was nmade whether or not<br />
to further subdivide each saubgroup based<br />
on any of the other available variables or to<br />
end the partitioning process by treating<br />
thenm as terminal groups. The statistical<br />
basis for this decision was deterniined by a<br />
set of stopping r ules. For any given gronup,<br />
the partitioning ceased when etiher one of<br />
the following conditions was mnet:<br />
1. The grrotip was not large enoughl to<br />
Warrunt anIother classificatiom, tlhat is, whllvl<br />
the ilnliilber of oihserfiltion>is in the groiup<br />
was less thani 100.<br />
2. None of the varialbles relducedl uniexplainil<br />
variation I)v at Ieast 1%, or<br />
((TSS -'I WSSQ)/TSSQ)*100 < 1 per<br />
cent.*<br />
Otherwise, the group was fuirther subdivided<br />
according to the criteria discuissed<br />
previously tor generating new, sulbgroups.<br />
In some cases, however, the process was<br />
terminated tor nonstatistical reasons regarding<br />
overall inanageability (e.g. inaintaining<br />
a low number of total groups) or<br />
medical interpretability.<br />
* This I per cent I>ouid was increased ii certain<br />
Major Diagnostic Categories.<br />
DC; :()NST'I'(:'i'ION<br />
Tlhis grotu),ping process resulted i¡ tihe<br />
lormatio, oí' :383 finai grolups or I)CG.s<br />
each defutied by somie set of the tollowing<br />
patient attributes: primary diagnosis, see-<br />
' ondiny diagnosis, primary surgical procedure.<br />
secontlary surgical procedure, age,<br />
and in one case, clinical service aiea. While<br />
other variables such as sex, tertiary diagnosis<br />
or surgical procediure were<br />
examtined, they were not imnild to be significiant<br />
iii explaining ouitput utilization. A list<br />
of these grotups with a brieft narrative descriptioei<br />
of their contents appears in the<br />
Ap)l)elctlix. A more ctiip)lete spetcification<br />
can be obtained fromn tlie Health Care<br />
Financing Administration.'<br />
The DRGs vary considerably in their<br />
structure across the iMajor Diagnostic<br />
Categories. Some Major Diagnostic<br />
Categories are not further subdivided,<br />
such as Category 35, Hemorrhoids, in which<br />
no variable demonistraited a sufficient efttct<br />
in further explaining outpitt uti lization. On<br />
the other hand, Appendicitis, Category 46,<br />
is ftirther subdivided on, the basis of<br />
specific primary diagnosis and the presence<br />
ot a secondary diagnosis. This restilts<br />
in 4 DRGs: appendivitis (without<br />
peritontitis) and without a secondary diagnosis,<br />
appendicitis (without peritonitis)<br />
with a secoudary diagnosis, appeidicitis<br />
(with peritonitis) without a secondary<br />
diagnosis, and appendicitis (with<br />
peritonitis) with a secondary diagnosis.<br />
This symmetric breakdown suggests that<br />
the effects of primary. diagnosis and the<br />
presence of a seconldary diagnosis are additive<br />
in nature. Major Diagnostic Category<br />
76, Fractures, has the nmost complex structure,<br />
resulting in 13 DRGs, indicating both<br />
the importance and interaction of 4 variables:<br />
primary diagnosis, secondary diagnosis,<br />
prinmary surgical procedure and age.<br />
It should also be noted that when variables<br />
are h.ghly correlated, very often only<br />
one applears in the classification for a<br />
specilic mnajor category. Asn extrieme exampie<br />
of this is Major Diagnostic Category 36,<br />
Hypertrophy of Tonsils aud AdeMoid,