ets exposure, lung cancer - Legacy Tobacco Documents Library

http://legacy.library.ucsf.edu/tid/wyk81f00/pdf
ASSE$SMEh? OF DISEASE STATUS
MisclissiGcation on diuase uatus occurs wbce diaposcs otber t .ban prinn cxscinotri of
tbe luag are induded in tbe easc series or .rbeo a primary eancer of tbe lubg is iucluded among tbc
contsols due to iu ksaviag 6one uadcteaed Garftakcl et &i . reponed that of 283 .+omcn listcd as
luving lu.ag ea,nar in bospita, rteords but sritb no mention of tDeir having r .n;,aked, 36 (12 .")rc)
tvrncd out to b.avc diWoeet oeber tbin Iuag eaacer wbcn the histologv .ras reviee+ed by one of thc
autisors (8) .
ln uud.ies in whicb kiixtotooc vcritieation of lt,tng ea .oeer is a eriterion for indusion in tbe
srudy, mi«liccifiution tbould bx minimaJ . Nov~rcvcr, tiomc of tbe uudies listed in Table 1 wcrc
lsc.king this for all cucs .
lt sbouild a1so bc mcntioncd that ev=a vbca luag a.ncer is biuologacally veriftcd, it is
posssble that t:omc eases judgcd to b~e pr~mary sa.nc.er of tbe lung arc aaually r~eeoadary io a cay :cr
of anotber sitc that bas gonc undete.ued
ASSF_SSMEhT OF E?t-FOSURP STATUS
This is a geater problcm tbas asussment of discasc status, and for somc i .nvestigators it
is tbc key problem of epidcmiofogic ctud .ies of ETS a.ad luag eanccr (9,10) .
Misclassi.ficat .ion of esposure szatus un occur in a Aumbcr of ways . F'ust, subjects p~o
bsvc t;mokcd for s.omc period of thcis lifc c.in be erroncously iacluded in a t;tudy of tacver smokcrs
Se .cond, subjcas may uadcr•repon (minimize) or over•repon (inllate) tbcir ETS exposusc, or this
may be done by proxies . A t.isird type of misrlassifrcauon ean occur .rben trome iadireu measu : c
(zucb as .rbcther tbc subjea is maNied to a smoker or bow mucb t4sc spouse amokes) is tued as a :z
iadicator of ETS exposure . The cffect of misclassificution oe abe estirnate of tbe RR depends on
Wbctbcr thc m'tsclassification is random or diffcrcntia) (tbat is tystcmatic) . Random misdissiTic•a ;ion
wilJ bias tbc estimate of tbe RR towud tbe taul .l, thus making an eFfeu, if tbere is one, more d ;uicult
to dcteu . If misrJassifieation oa ezposurc differs ber*'cte eases asd eoatrols, tbe estimste of the RR
ca.n be bi.ased eitbcr upwuds or dovrnwards dcpendiag on the d'ueuion of t .bc bi.as (11) .
MLSclGJS(fica.rion of Acr1vC sr/loktrl a.t f1CYtr Jrrloklr3 .
Garfinkcl and eo- .+orkers found that among lung eancer w .es ideatiTed as 'saonsmokcrs'
or lacki.ng aay mention of t:moking in the bospital reeord, 40% vcrc revule.d to have smokcd up, n
reinterview (8) . AJtbougb a detailed persana] interview yields more acGwatc ssnokiag histories tba:
reliince on bospital ebarts, it is sti11 likcly that, evtn .+bcn eubjc= are diruxly intenicwcd and morc
w*?bca various prwoes ase ttud, aomc miulsssification of ttmokers as ootumokers Dccurs .
Let his argued that random misrlassificatioa of emokers as aoa•uaokers eouple .d witL a
tendcnry of t:mokcrs to marry tsmokers eould account for the obscrved usocat .ion of aspousc's
znoking and iace .ascd lung canr:er risk in non•smoking :pouses (9) . Lssuming a SCr
ci •t~~~__iFiution of amok.ing subje.cts, a RR of 2D for aa .ivc smoking„ no truc eficct of passivc
tmol`in& and a betwcen•tpotuc tmoking concordance of 3,