BOOKS OF RtfiDIfGS - PAHO/WHO

CREENLAND iT AL
- 105 -
TABLE 2. Fiacturs Exuri.iwed i r
ColtlribltiHn tul h ilri teielit
Death Raite Dillcsruic'
Maternmal ae (yeAr1)
Raie/ (Black; Hipanic; other)
Cnavidity
Numli.r of dpl ,umneous abor.ltís (20 weeLk
Prenatal cue (yes; no)
Hydramiios (yes; no)*
Abnoeroll presentation (yes; no)
Cord prolepie (yes; no)
PlMaenta abnormalties (bruptio, previa, etc.)
(yes; no)
Oiyutoin (no; augimetaiuun; ieduciuil)*
Vaginal delivery (no; ueouplica(ed;
complicated-braech, moldfocepa. vacuu¡m, faled
forcepa or vauuim. etc.)
C-sectiou (no; repeat or pnriauy elective;
nonelective)
Abnormal dugnton ofaibor(no; 20 hn
Seu
Birthweight (grais)
Cesattional age (Dubowitz) (weeks)
Apar I iian. (by pediasticui)
ApSar 5 inio. (by pedimcri¢ia)
eauscattion al deolvery tendotra(chei
intubatlon; no)
VMor consenital abormality. ch(uroounie/genetic
defect. etc. (no; yes, potentially viebl)
slteliratory dintrins syndrumaneresiriatory miilure
(uaswtlated with tmmiuunty andlur pernna)
ap.ipyua) ('es; no)
Meuniunm/biluduasnintic fluid spiratioia (ye; no)
Provel iel(e.tiun (no; cougeni il or neonalal. Ro<
horsiital.acluired) (infctiuns frli bo' .e of
nouuuomiial oriyin-e.la. buterial sepuis with
unire >3 dary pu)dielivery-were cuded "no"e
ls;oi uiiiioíiiítiofsi4ther ígyoKeniral hernmlytic
disorder req lirings exlchanl tria slusoiu)(yes; no)
Signifiiclat iirth trautuilitjury s c; no)
iirJtl oof hospital (home. iln raiulit. etc.) (yes; no)
Nuiber ol' da»y in hospital (0-24. hr> . I day)
'l'. ltac, tBiis silflred Irdsn ¥ ib levecls f r eímrdilag
iluacuracy iii dte recirds esauIalUleLd
Discussion
MiDICtAL Ci
Plrolpr applicatio of tlihe cUse.uitrol
approach requires consideratiou of and
concerted efforts tou meet a number of
criteria for study (internal) validity. These
criteria have been extensively discussed
asid systemiiatzed li¡ tihe recent epi-
- "
demiologic literature.. Chief amolg
the criteria have been selection validity
criteria (concerning bias in selection),
inlormation validity criteria (concerning
dite quality of the inilfianatíio on the risk
factora under study) and couiparnson validity
criteria (concemrning the control of confounding).
Efforts should be made to meet
these criteria as far as possible in any area
ofapplication ofthe case-control method. A
researcher considering a case-control appnrach
should carefully evaluate whetlser
his study setting would allow fulfiliment of
the various validity criteria. If selection.
informnation arid comnparison valility
criteria cannot be met. the study will be
unsound. These criteria apply to recordbased
cohort ("historical prospective")
studies as well.
Special caution is required in the use of
routine medical records for case-control
'and historical prospective studies, sinee
biased recording of information on the
study subjects will produce corresponding
biases in tdie study results. Investigatnrs
must be alert to the possibility tthat the use
of a particular treatment regimen led to a
more frequent recording of the outcoimte
under study or thbat the treatement under
study was recorded more freqmaently
mutiong tbose experiencilig the outconle.
These were clearly not possibilities in our
NICU study (where the "treatment" was
the NICU). but such problenms are frequent
in nonexperimental drug evaluations."
Impoortant in any mionexperinientil shady
of mnedical treatments or technology will
be txontrol of l'cnfounding.a Conflmntditlg
warrants special attention in nonexperilmelntal
ttclisuolohgy eva;ltl;itioi lIi.calibt' o
tdie possiility ,l "cbu¡llouldinig by itídli.tioín"i";
this (otic'rs whenever prognostic