community sheet #3 of dr.faroo2-thara2 m3ulla

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community sheet #3 of dr.faroo2-thara2 m3ulla

Post by Dyala Al-Armouti on 6/5/2011, 4:28 pm


In the Last two lectures we were talking about epidemiology .. today we are going to talk about uses of epidemiology … which is finding out the frequency and determinants of a disease.. we also talked about risk factors and measures of risk..

We have absolute measures.. like incidence , prevalence , …

An important measure of risk is correlation coefficient .. (R) value ..

The R value can do from (-1 ) ---------> (+1 ) so it goes through zero .. as the value approach zero .. this means that it becomes unsignificant .. meaning that these two variables have no significant relationship between them..

So if we take a value near the zero for example 0.1 OR -0.07 so these two values as an R values these two are considered unsignificant values bcz they are very near to the zero ..

When we say that the value is between -1 and zero .. that means that we have a negative correlation..

** Negative correlation mens : if one value of a variable increases .. the other variable decreases..for example ::::: as income of the family increases .. number of illnesses per year decreases ..

Whereas .. the positive correlation means : if one value increases the other value will also increase.. for example .. if # of cigarettes smoked daily increases .. the probability of lung cancer and bronchitis will increases ..

SOo wt we should know about the R value that it’s a relation rather than a calculation ..

Attributable risk percentage or population attributable risk percentage .. the dr. asked us bring some info about it .. so I checked it .. nd I found that :
Attributable risk percent (ARP) is a calculation that can be derived from attributable risk and It gives the portion of cases attributable (and avoidable) to this exposure in relation to all cases.

If we go back to literature we will find that they say that this sample or the case control study was conducted to find out the cause the relationship between two variables.

We have 2 major types of epidemiological studies :

1. Observational (derasat r8abyye)

a. Descriptive (derasat wa9feyye) àdescribe occurrence of disease according to person , place, and time .. for example .. infectious diseases are more common in children than in adults .. ( we are describing the occurrence according to age ) OR when we say that myocardial infarction from 40-50years is more fatal in males than in females (here description is according to sex) OR when we say that prevalence rate of diarrhea in children in Jordan is higher in summer when compared to other seasons ( description according to time)

** the main type of descriptive studies is the Cross-sectional studies.. (derasat ma86a3eyye) it’s the most common type in Jordan and the region .. whY ?? CZ ITS VERY EASY AND CHEAP TO CONDUCT.. y3ne mathalan bna5od 3yyene mn class ..15 wa7ad bnes2alhom eza 3ndhom sore throat or not .. so here we can get the prevalence rate of sore throat in this class ..

This type of studies has 2 major objectives : 1. Find out prevalence rate of a disease..
2. Find out risk factors .

We learned how to get the prevalence rate nd risk factors of disease in previous lectures ..

Risk factors are significantly associated with the occurrence of the disease ..

AS A GENERAL RULE !!!! à significant MEANS T value < or = 5% (0.05)

b. Analytic : to analyze factors behind the or of occurrence of disease .. for example .. about myocardial infarction .. ‘’why MI is more fatal in males than females.. ‘’ !!

AnalytiC studies are of 2 types :

1. Follow up studies (cohort) >> derasat tatabo3eyye.. O.o >> 2 objectives : 1st is to find incidence of a disease and the 2nd is to find the causation (cause effect) relationship..

2. case control studies.. ( deraset al 3ayyeneh wl majmoo3a al dabe6a ) !!!!

Soooo here we have 2 grps .. 1st one is the case which have the disease under investigation .. and the 2nd grp is the control grp .. the comparative grp cz we always compare cases with other grps .. HERE we only have one objective that is to investigate cause effect (causality) relationship..,.

We have 5 criteria for causation but we r only interested in the 1st criteria which is the TYPE OF STUDY.. >> bneshra7ha b3deen -_-

So we investigate cause effect by 1. Cohort and 2. Case control ..

2. Experimental studies (derasat tjrebyye 3la el human) to find out 3 different things : 2 types .. :

a. clinical trials .. which is common >> more sophisticated //example : in Jordan they made a clinical trial on drug called healer ointment .. for hemorrhoids.. >> one of best drugs over world .. xD 7tta mawjood bel jwaideh :P

b. community trials .. not very common .. (fluoride story J )

what are the 3 objectives of the experimental studies ??

Find the incidence rate of a disease ..

Find the cause / effect relationship..

Find the efficiency / efficacy rate of intervention ..
Y3NE mathalan lamma y2olna what is the efficacy rate of ampicillin in treating septicemia !! J
Or mathalan efficacyrate of protogel!! In treating abcesses ..or efficacy of poilo vaccine in treating poliomyelitis.. >> all of these are experimental .. J

A Q was asked .. what is the difference between community and clinical trials ??
>> Community trials : fluoride issue in japan .. there was some villages have fluoride in their drinking water ,, and some villaes don’t .. so they found that the incidence of dental caries in villages with fluoride in their water was very low compared to other villages .. so here we took communities and compared all ppl in them … amma el clinical trials : we mean individuals .. mathalan bn7ki enno there is a vaccine for soar throat experimented on animals .. we want experimental human grps and test this vaccine on part of them .. then we compare it with the grp who didn’t take the vaccine .. nd make follow up for them .. then we obtain the value ( incidence rate ) of sore throat .. 2 incidence rates .. b6ale3elhom relative risk and obtain T value ..
Here the dr ballash y7asseb ar8am i couldn’t recognize wt he is talkin’ about ,, bas he said enno bdna n6alle3 2 incidence rates .. o mnhom n6alle3 el relative risk J and we obtain the (t) value which test the difference between the two percentages ..

Here O_O >> why we didn’t use the T student test ??????!!!!
Cz we use it when we have 2 different means.. but when we have percentages we use chi-square test.. from fisher exact probability test …

If we want to find out the incidence rate of A specific dental disease in a specific community wt type of study should we use ????
We use cohort study and experimental study

If we want to find out the cause /effect relationship .. investigate it by ??
Cohort study .. case control study .. and experimental study J

v So2al xD >> IN any experimental stusy .. is it fair to scarify few individuals in a study ?? el Dr. by2ool YEssS .. he said sth about el 7a9beh zaman kef kanat fatal (kanat to79od el 26fal) nd by this time it becomes a very mild disease J

W “ salaaaaaameh” tsalemkom … stdy well .. o ya rb ne5l9 3la 5er J

DONE BY : TharA’a MuALLa

Dyala Al-Armouti

عدد المساهمات : 639
النشاط : 16
تاريخ التسجيل : 2009-09-06
العمر : 26

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