SAO PAULO
D IC A L
O U R N A L
Alvaro Nagib Atallah*
The appraisal of medical scientific evidence
*
MD, PhD, MSc, Associate professor of Internal Medicine of Escola Paulista de Medicina,
President of the Latinc/en Latin American
Clinical Epidemiology
Network.
A
n y d o c to ro n th e b e s t e x is tin gw o u ld p r e f e rs c ie n tif icto b a s e h is th e r a p e u tice v id e n c e . W e c o u lda p p r o a c hn a m e it M A B B E E - M e d ic a l A p p r o a c h B a s e d o n th e B e s t E x is tin g E v id e n c e . T h e p r o b le m is h o w to d e f in e w h a t is g o o d s c ie n tif ic e v id e n c e a n d w h a t is n o t. W e u n d e r s ta n d th a t n o w a d a y s th e r e is r e a s o n a b le c o n s e n s u s o n a c c o u n ta b le m e th o d o lo g ie s f o r th e c r itic a l a p p r a is a l o f m e d ic a l lite r a tu r e . T h e r e a d e r m a y e a s ily f in d th e m in th e lite r a tu r e o f th e s e la s t tw o d e c a d e s ( 1 ,2 ,3 ,4 ,5 ,6 ) , a n d im p r o v e h is /h e r s k ills th r o u g h th e A m e r ic a n C o lle g e o f P h y s ic ia n s J o u r n a l C lu b , w h ic h is a s u p p le m e n t to th e A n n a ls o f I n te r n a l M e d ic in e .H o w e v e r , it is im p o r ta n t to p o in t o u t s o m e f e a tu r e s o f th e m o d e l o f th e s tu d ie s w h ic h g e n e r a te th e e v id e n c e s to a llo w th e d e v e lo p m e n t o f " M A B B E E m e d ic in e " . T h e r a n d o m iz e d d o u b le - b lin d c o n tr o l tr ia l w ith a n a d e q u a te s a m p le s iz e a n d q u a lity c o n tr o l is th e id e a l d e s ig n to c o m p a r e p la c e b o to a n y tr e a tm e n t, o r d if f e r e n t ty p e s o f c lin ic a l o r s u r g ic a l tr e a tm e n ts . A lth o u g h th is s e e m s o b v io u s , it h a s s till n o t b e e n w id e ly a p p lie d to m e d ic a l p r a c tic e in th is c o u n tr y . R e a s o n in g b a s e d o n e x p e r ie n c e , c a s e r e p o r ts , a n d r e tr o s p e c tiv e s tu d ie s a r e s till v e r y c o m m o n in M e d ic a l J o u r n a ls a n d m e e tin g s .
A n o th e r m e th o d o f o b ta in in g g o o d e v id e n c e is th e s y s te m a tic r e v ie w o f m e d ic a l tr e a tm e n ts f o llo w e d b y a s ta tis tic a l s u m m a r y n a m e d m e ta - a n a ly s is . T h is ty p e o f r e s e a r c h s h o u ld in c lu d e a ll th e p u b lis h e d a n d u n p u b lis h e d c o n tr o lle d c lin ic a l tr ia ls w ith g o o d s ta n d a r d s . T h e ty p ic a l o d d s r a tio - th e f in a l r e s u lt - u s u a lly r e p r e s e n ts th e b e s t e v id e n c e r e g a r d in g th a t s p e c if ic tr e a tm e n t u n til th e m o m e n t th e m e ta - a n a ly s is w a s p r o p e r ly c o m p le te d . H o w e v e r th e c o n s is te n c y o f th e r e s u lts d e p e n d s o n th e c lin ic a l tr ia ls f o u n d in th e lite r a tu r e . P u b lic a tio n b ia s , w h ic h is th e te n d e n c y b y s o m e jo u r n a l e d ito r s n o t to p u b lis h c lin ic a l tr ia ls w ith n e g a tiv e r e s u lts , a f f e c ts n o t o n ly th e a u th o r s s u b m ittin g th e p a p e r s b u t a ls o th e s y s te m a tic r e v ie w p r e p a r a tio n , a n d f in a lly th e d o c to r s in te r e s te d in th e b e s t e v id e n c e - b a s e d m e d ic in e , w h ic h , a s a c o n s e q u e n c e , a f f e c ts th e p a tie n ts .
P r o s p e c ti v e c o h o r t s tu d ie s a r e m u c h b e tte r th a n r e tr o s p e c ti v e s tu d ie s , b e c a u s e th e y a llo w f o r s tr o n g e r c o n c lu s io n s . A p r o s p e c tiv e s tu d y p e r f o r m e d in d e v e lo p in g c o u n tr ie s h a s b e tte r c h a n c e s o f e a r n in g c o n f id e n c e .
D ia g n o s tic te s ts m u s t b e a s s e s s e d r e g a r d in g th e ir u tility . T h a t m e a n s th e a d o p tio n o f a n e x c e lle n t g o ld s ta n d a r d , d e f in itio n o f c u t- o f f p o in ts , c a lc u la tio n o f s e n s itiv ity , s p e c if ic ity , a n d p r e d ic tiv e v a lu e s , a n d d e s c r ib in g c o n f id e n c e in te r v a ls .
C o m p a r is o n s w ith a tr a d itio n a l d ia g n o s tic te s t ( R e c e iv e r O p e r a tin g C h a r a c te r is tic s - R O C ) c a n a ls o b e m a d e . F o r m o r e d e ta ils th e r e a d e r m a y b e r e f e r r e d to ( 2 ) a n d ( 6 ) .
I n o th e r w o r d s , g o o d c lin ic a l r e s e a r c h d e p e n d s o n th e u s e o f c lin ic a l e p id e m io lo g y a n d th e a d h e r e n c e to v e r y w e ll-d e s ig n e ll-d s tu d ie s , w h ic h ta k e in to a c c o u n t th e p r e v e n tio n o f b ia s a n d th e a p p lic a tio n o f a p p r o p r ia te s ta tis tic a l m e th o d s .
W h e n r e a d in g a s c ie n tif ic p a p e r tr y to id e n tif y th e f o llo w in g p o in ts :
1 . W a s th e r e a c le a r a n d s im p le r e s e a r c h q u e s tio n ?
2 . W a s th e s tu d y d e s ig n a p p r o p r ia te to a n s w e r th e q u e s tio n ? 3 . W e r e th e in c lu s io n a n d e x c lu s io n c r ite r ia o f s tu d ie d p a tie n ts
c le a r ?
4 . W e r e th e r e a c c e p ta b le d e f in itio n s f o r th e d ia g n o s e s a n d th e o u tc o m e s ?
5 . W e r e th e s a m p le s iz e a n d th e s ta tis tic a l p o w e r c a lc u la te d ? 6 . W a s th e r e g o o d q u a lity c o n tr o l o f , f o r e x a m p le w h e n
a n a ly z in g c lin ic a l tr ia l: f r e q u e n c y o f d r o p - o u ts , a d h e r e n c e to th e tr e a tm e n t a n d to th e r a n d o m iz a tio n p r o c e s s , c o -in te r v e n tio n , a n d c o n ta m in a tio n p r e v e n tio n ?
7 . W e r e th e s ta tis tic a l a n a ly s e s a p p r o p r ia te to a n s w e r th e m o r e r e le v a n t a s p e c ts o f th e r e s e a r c h q u e s tio n ?
8 . W e r e th e c o n c lu s io n s b a s e d e x c lu s iv e ly o n th e s tu d y r e s u lts ?
W e c o m e b a c k a g a in to th e c r itic a l a p p r a is a l o f m e d ic a l lite r a tu r e .
S o , in o r d e r to p r a c tic e M A B B E E M e d ic in e , o r E v id e n c e -B a s e d M e d ic in e , a ll d o c to r s - a n d n o t o n ly M e d ic a l J o u r n a l e d ito r s - w ill n e e d to b e f a m ilia r w ith th e e s s e n tia ls o f c lin ic a l e p id e m io lo g y in th e f u tu r e .
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