BOOKS OF RtfiDIfGS - PAHO/WHO

Vol XIX. No. o
- 104 -
Iil'e or tntislkrred into our out of the NICUs
were excluded in>)m the study. Very lew
inLaits Iruom either NICU were translerred
out.)Tlhere were 361 eligible iadniisi¡us to
uits A and I over dithe study peridl ( IY9J (u
unit A ¡id 162 to unit Bi). Of diese. 61
suflered neonatal death and thus became
the study cases, while 150 of the 300
suarvivors were selected fir the eointrol
(relcrenue) group.
The initial results are sunmarized in
Table 1. The crude ratio of the rUtes between
the units, 1.9, was signifiant at t the
0.(. level, faiirdy well ruling out chance
aloune as an explanation of the diflference
(Table I). Thle m¡ethoad uf rte computation
is brietly described in the appendix. Using
both univariate and multivariate statistical
techniques, ' 4 more than 30 risk fatours
were exwrnined as possible contributurs to
die ditierence. These are listed in Table 2.
Few tumed out tu be of any inmportanuce,
mtot Lbecuse of being similarly distributed
between the units. and sume because of
their very weak ctontribution to risk of
death. Ethnicity (race) was distributed
quite differently between the unm and
nearly all of dhe interunit differenee in
death rates was concentriated in the premature
infants (les dthan 1500 grnams birthweight).
After adjusting for race, the rate in
unit A was nmore tdiu three times die rate in
unit B among prematures, and the absolute
rate differences were quite high in this
group (more than 35 p>er ceit). Table 3
sulniaurizes thiese details. Further i nvestigatiln
of the elev::.'ed rutes in unit A will
benetit by this initial elimination ofseveral
ix>ssil)le explanations (such as ethnie diflerences)
aiad will be able to lcus ou. risk
iLwtors and aspects of care that primllrily
alieSt premature inlants.
Olher Conideraiiiau
A majior claas orflrolhletis in cas-cuaultnol
statli