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RADIATIONRADIATIONEPIDEMIOLOGYEPIDEMIOLOGYAND LEUKEMIAAND LEUKEMIA
B.Ledoshchuk, M.D.,Ph.D.
Institute of Epidemiology
Research Center for Radiation Medicine of Ukraine
Kyiv-2001
EPIDEMIOLOGY OF LEUKAEMIAEPIDEMIOLOGY OF LEUKAEMIA
Results of the 10-year study of leukemia among the
Chernobyl accident clean-up workers in Ukraine
1986-96
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
EPIDEMIOLOGY studies the occurrence and prevalence of
diseases among population identifies disease cases determines probable relationship between
various risk factors
AUSTRALIA12
USA89
CANADA13
ENGLAND14
WESTERN EUROPE
26
AFRICA-ASIA5
UKRAINE1
UNIVERSITIES AND INSTITUTES OF EPIDEMIOLOGYUNIVERSITIES AND INSTITUTES OF EPIDEMIOLOGY
Types of Epidemiology medical pharmaceutical veterinary environmental insurance
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Classification of medical epidemiology
•Infection epidemiologyInfection epidemiology
•GeneralGeneral epidemiologyepidemiology •Environment epidemiologyEnvironment epidemiology
•Clinical epidemiologyClinical epidemiology
•Military epidemiologyMilitary epidemiology
•Epidemiology of insuranceEpidemiology of insurance
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Main types of epidemiology researchMain types of epidemiology research
MOLECULAR
REPRODUCTIVE
ENDOCRINOLOGICAL
PROFESSIONAL
ECOLOGICALCARDIOLOGYCAL
ONCOLOGICALSOCIAL
Methods of analytical epidemiology
Cohort Case control Combined
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Methods of analytical epidemiology
Cohort study, Follow-up studyInvestigation for a certain period of time of a Investigation for a certain period of time of a
group of people defined prior to onset of disease group of people defined prior to onset of disease
•Registration of new disease casesRegistration of new disease cases•Exposed group (clean-up workers-86 )Exposed group (clean-up workers-86 )•Unexposed group(clean-up workers-87, 88-90 )Unexposed group(clean-up workers-87, 88-90 )
There is a risk of healthy worker effect in comparison with There is a risk of healthy worker effect in comparison with population (underestimation IR in exposed group)population (underestimation IR in exposed group)
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Methods of analytical epidemiologyCase/control studies
•Investigation of groups of people defined by Investigation of groups of people defined by presence or absence of diseasepresence or absence of disease
•CaseCase - ( - ( patientpatient) ) exposed and unexposedexposed and unexposed•ControlControl - ( - (healthyhealthy) ) exposed and unexposedexposed and unexposed•Only estimation of relative risk is possibleOnly estimation of relative risk is possibleRR (relative risk) orRR (relative risk) or OR OR ((odds ratioodds ratio))
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Goal of research ::Define the dependenceDefine the dependence of incidence of of incidence of leukemia among Chernobyl accident leukemia among Chernobyl accident clean-up workers (ACW) on the year clean-up workers (ACW) on the year of participation in emergency works of participation in emergency works and period of time that passed since and period of time that passed since exposure to radiationexposure to radiation
Results and discussion• Subject of observation: Subject of observation:
Chernobyl accident clean-up workers Chernobyl accident clean-up workers (ACW), males, included in State (ACW), males, included in State Chernobyl Registry of Ukraine. Chernobyl Registry of Ukraine.
• The number of persons under study at The number of persons under study at the end of the observation period the end of the observation period
is is 179 026 . .
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Sources of information• State Registry of victims of State Registry of victims of Chernobyl Chernobyl
accident accident (CA)(CA)
• specialized registries and subregistriesspecialized registries and subregistries• primary data from medical clinicsprimary data from medical clinics• data of official disease registration and death data of official disease registration and death
cases registrationcases registration• special selective registration of casesspecial selective registration of cases• data of expert commission for victims of CAdata of expert commission for victims of CA
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Main sources of information for case search:
Results of annual medical examination of ACW
Regional hematological clinics data
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Main methods of obtaining of information :
•retrospective
•current
•passive
•active
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Period of observation ACW:1987-1996
Calculation were performed for 5-year intervals
1987-1991, 1992-1996
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Diagnostic criteria - under-record of cases due to strong
diagnostic criteria - over-record of cases (including
irrelevant to the diagnosis cases) due to insufficient demands to diagnosis
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Classification of Classification of diseasesdiseases
Choice: EtiologypatogenesesLocalizations disease ICD-9 or ICD-10Clinical (FAB) Classification of
Leukaemia
• ssubjectiveubjective, o, objective symptoms; outcomes of bjective symptoms; outcomes of laboratory and tool researcheslaboratory and tool researches• Diagnostic criterions (the majority of Diagnostic criterions (the majority of diseasesdiseases has no has no precise criterions)precise criterions)• Classification of Classification of diseases diseases ((in case of in case of indeterminacies; indeterminacies; vague, not updated cases)vague, not updated cases)• Reliability of the diagnosis - Reliability of the diagnosis - autopsyautopsy ( (typestypes of of researches)researches)• interpretation errorinterpretation errorss of classification of classification
Reliability of the DiagnosesReliability of the Diagnoses
the Factors influencing the quality of the diagnoses
Reliability of the DiagnosesReliability of the Diagnoses
Strict selection of cases
Loss of true diseases
Soft selection of cases
Deriving cases not have significance
GipoGipo diagnosticsdiagnostics
GiperGiper diagnosticsdiagnostics
Sensitivity and specificitySensitivity and specificity
Under the sensitivity one understand probability that,the patient canl be classified as the patient
Number of the patients classified as the patients
Se = Total number of the patients
Under the specificity one understand to probability that healthy can be classified as healthy
N umber of Healthy, classified as healthy
Sp = Total number of healthy
MODEL of SENSITIVITY And SPECIFICITYMODEL of SENSITIVITY And SPECIFICITY A. Ahlbom, S.Norel 1990A. Ahlbom, S.Norel 1990
The populationThe populationThe patients ClassifiedClassified ccs the patientss the patients
The patients The patients cclassifiedlassifiedaas healthys healthy
(Is falseNegative)
HealthyHealthy cclassified lassified
aas the patientss the patients
(Is false Positive)
The patients The patients cclassifiedlassified aas the patientss the patients
Information flows between institutions Information flows between institutions and the centerand the center
•ccCITY HOSPITALCITY HOSPITAL•DDDDISPENSARYISPENSARY
OBLAST HOSPITAL OBLAST HOSPITAL OBLAST DISPENSARYOBLAST DISPENSARY
INSTITUTIONAL INSTITUTIONAL HEMATOLOGICAL HEMATOLOGICAL DEPARTMENTSDEPARTMENTS
CENTER FOR RADIATION MEDICINE
Information exchange for Information exchange for quality controlquality control
TECHNICIAN
EPIDEMIOLOGIST
D/B
SUPERVISER
LEUKEMIA DIAGNOSIS STRUCTURE
There are 48 cases of leukemia
among clean-up workers of 1986 • 13 – acute leukemia - AL (27 %),• 20 – CLL (42 %),• 14 – CML (29 %), • 1 – other forms of leukemia (2 %).
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
LEUKEMIA DIAGNOSIS STRUCTURE
There are 15 cases of leukemia among clean-up workers of 1987• 8 cases of AL (53 %),• 2 cases of CLL (13 %),• 4 cases of CML (27 %), • 1 case of unspecified leukemia (7 %).
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
LEUKEMIA DIAGNOSIS STRUCTURE
There are 8 cases of leukemia
among clean-up workers of 1988-90 • 1 case of AL ,
• 4 cases of CLL,
• 3 cases of CML.
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
LEUKEMIA DIAGNOSIS
STRUCTURE
0%10%20%30%40%50%60%70%80%90%
100%
1986 1987 88-90 Total
Unspecifiedleukemia
CML
CLL
AL
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
• Crude measure – calculated for population as a whole
• Specific measure – calculated for specific groups of population
• Standardized measure – for completion of summary comparison between two or more groups diversified according to age or other criteria
Generate rate • Absolute rate (number)
• Popularity
• Morbidity
• Mortality
• Expressed as cases from 106 to 103 in investigated cohort (case/control)
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Popularity prevalence rate, ratio - PR
• It is a quota of morbidity among population in certain moment of time
PR = number of existing cases of disease
population during the same of time period
B
A
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Morbidity
incidence rate - IR Represents rate at which new cases are Represents rate at which new cases are
occurring.occurring.
• IR IR = = number of new cases of disease over a specified time period number of new cases of disease over a specified time period
person-years, person-time, time at riskperson-years, person-time, time at risk
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
CUMULATIVE INCIDENCE
• cumulative incidence rate - CI• It is a quota of healthy persons that can fall ill
during a certain period of time
• CI = number of new cases over a specified time period
population at the beginning of a specified time period
• , where IR – incidence rate – duration of observation period
tx IR CI
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
confidence intervalconfidence intervalCalculation of 95% confidence intervals forCalculation of 95% confidence intervals for
• prevalence rate (PR)prevalence rate (PR)
• cumulative incidence rate (CI) cumulative incidence rate (CI)
• incidence rate (IR)incidence rate (IR) IRIR1.96 (R- person-years)1.96 (R- person-years)
R
IR
NPRPR
PR)1(
96,1
NCICI
CI)1(
96,1
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
confidence intervalCalculation of 95% confidence intervals for
• relative risk
where where e e - logarithmic base = 2,718- logarithmic base = 2,718ln - logarithmic function with e base (ln - logarithmic function with e base (natural natural
logarithm)logarithm)ln(RR) - survey numberln(RR) - survey number = square root of dispersion var = square root of dispersion var
calculated numbercalculated number]var[ln(RR)
e ]var[ln(RR)1,96ln(RR)
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Calculation of Relative RiskFor cumulative incidence RR=(A1/N1)/(A0/N0)
where А=number of cases
N=number of person year
95% confidence interval for relative risk ln(RR)-dispersion
var[ln(RR)] =[(N1-A1)/(N1*A1)]+[(N0-A0)/(N0*A0]
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Calculation of Relative RiskFor incidence rate RR=(A1/R1)/(A0/R0)
where А=number of cases
R=number of person-years
95% confidence interval for relative risk
ln(RR)-dispersion
var[ln(RR)] =(1/A1)+(1/A0)
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Stratification• Division of the population into subgroups (strata) Division of the population into subgroups (strata)
if there is the base to assume that the incidence is if there is the base to assume that the incidence is unequal in different groupsunequal in different groups
• strata distribute according to:strata distribute according to:– ageage– sexsex– occupationoccupation– radiation doseradiation dose– other effectsother effects
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Standardization- is one of the method of comparison validity
• direct method of standardization
• indirect method of standardization
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Direct Method of Standardization
• within group, intergroup and international standard within group, intergroup and international standard age is used for comparison of incidence rates in two age is used for comparison of incidence rates in two groupsgroups
• ratio of standardized incidence rates is presented by ratio of standardized incidence rates is presented by formulaformula
(R1.1/R1.n)*RR1.1+(R1.2/R1.n)*RR1.2=ASR1(R1.1/R1.n)*RR1.1+(R1.2/R1.n)*RR1.2=ASR1
(R2.1/R2.n)*RR2.1+(R2.2/R2.n)*RR2.2=ASR2(R2.1/R2.n)*RR2.1+(R2.2/R2.n)*RR2.2=ASR2
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
indirect method of standardization
SIR(O/E)*100 (standardized incidence ratio SIR)
• ratio of O-observed number of cases at exposed group and E - expected number of cases at control group
• standard age of exposed group is used for comparison incidence rates in two groups
E= (N1*IR1)+(N2*IR2)
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Distribution person-years of observation by age groups among CWA(full period, 1987-1996 )
Year of clean-up work Age group
1986 1987 1988-1990 1986-1990 20-29 128 470 52 439 4 180 185 089 30-39 336 877 165 222 111 563 613 662 40-49 187 467 98 292 93 248 379 007 50-59 74 242 13 070 4 437 91 749 60-69 20 021 2 291 568 22 880
TOTAL 747 077 331 314 213 996 1 292 387
Distribution of person-years of observation by periods
Year of clean-up work Period of observation 1986 1987 1988-
1990 1986- 1990
1987-1991 292 823 127 330 57 020 477 173 1992-1996 454 254 203 984 156 976 815 214 1987-1996 747 077 331 314 213 996 1 292 387
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
.Age distribution of the leukemia diagnosed CWA under study in 1987-1996
Year of the clean-up work Age group 1986 1987 1988-1990 1986-1990
20-29 4 1 1 6 30-39 7 5 3 15 40-49 15 7 3 25 50-59 18 1 1 20 60-69 4 1 0 5 20-69 48 15 8 71
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
-Number of cases from 20 to 29 years/1000,000 clean-up workers of 1986 - А1 1987г. – B1
-Number of males from 20 to 29 years/100,000 clean-up workers of 1986 - A2 1987г. – B2
CalculationFor clean-up workers of 1986 A1*(12,000/A2)=ASR1
For clean-up workers of 1987 B1*(12,000/B2)=ASR2 where 12,000 – world standard in this interval
Age Standardized Rate (per 100.000)
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Distribution of the leukemia diagnosed in CWA under study in 1987-1996 by periods of
observation
Year of the clean-up work Period of
observation 1986 1987 1988-1990
1986-1990
1987-1991 22 6 1 29 1992-1996 26 9 7 42 1987-1996 48 15 8 71
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
Results of Standardized Leukemia Incidence Ratio calculation for CWA of 1986 versus CWA of
1987 by periods of observation.
Period of observation SRR1/SRR2 (95 % CI)
1987-1991 3,32 (1,08; 10,20) 1992-1996 0,69 (0,15; 3,05) 1987-1996 1,00 (0,29; 3,42)
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
- COHORT data are presented as relation risk estimation RR=IR1 / IR0 where IR1 and IR0 are incidence coefficients A1 and A0 - number of cases
R1 и R0 - person-years at risk
Design formulasof relation between exposure and incidence
RARA
00
11
/
/
IRIR
0
1RR
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
- CASE-CONTROL relative risk estimation - odds ratio (OR) where A1=a, A0=b R1=c, R0=d A1 and A0 - number of cases
R1 and R0 - person-years at risk
Design formulasof relation between exposure and incidence
bc
ad
dc
ba
OR
GENERAL EPIDEMIOLOGYGENERAL EPIDEMIOLOGY
Sources of Radiation ExposureSources of Radiation ExposureFrom NCRP Report No: 93
3%1% 4% 11%
26%
55%
Radon Natural Sources (ex.Radon)Medical X_rays Nuclear MedicineConsumer Products Other
ATOM PRINCIPLE DIAGRAM ATOM PRINCIPLE DIAGRAM ((Craig C. Freudenrich,2001, HAW)Craig C. Freudenrich,2001, HAW)
ElectronElectron
NucleusNucleus
OrbitOrbit
PENENTRATING RADIATIONPENENTRATING RADIATION
Radiation Source Alpha Particles
Beta Particles
Gamma Rays
Stopped by a sheet of paper
Stopped by a layer of clothing or by a few millimeters of a substance
Stopped by several feet of concrete organic tissue or a few inches of lead
RADIO-BIOLOGICAL EFFECTSRADIO-BIOLOGICAL EFFECTS
NOT STOCHASTIC EFFECTS•as a result of high irradiation acute
radiation sickness and furnaces radiation injuries are developed
STOCHASTIC EFFECTS
•developed during prolonged irradiation (external, internal, balanced, critical organs etc.) Somatic, genetic, embryo toxic
STOCHASTIC EFFECTS•Somatic and genetic, embryo toxic effects
are developed in casual, probabilistic nature•Only probability of damage appearance
depends on dose, but not weight and depth of damage
•Frequency of appearance radiation-induced diseases increases with dose increase
RADIO-BIOLOGICAL EFFECTSRADIO-BIOLOGICAL EFFECTS
STOCHASTIC EFFECTS
•Summary stochastic effects during population irradiation (population group) are defined by collective dose
•It is impossible to define an individual effect or additional risk and it is impossible to determine which kind of cancer is typical for additional cases
RADIO-BIOLOGICAL EFFECTSRADIO-BIOLOGICAL EFFECTS
MODELS of MODELS of EXCESSEXCESS of of RISKRISKSS
D.Pierce, D.Preston, 1996-1999D.Pierce, D.Preston, 1996-1999
Time dependent models of redundant relative risk for solid swellingsLimit of models of risk for a cancer = 10 years
Absolute risk for leukaemiaLimit of models leukaemia = 2 years
The limit of models of risk is a concept latent Period - between the beginning of effect of the radiation factor and diagnostics leukaemia
Execes Execes absolute risk for absolute risk for leukaemialeukaemia
Where Where and and - constant: - constant: - depends on - depends on categories categories --Age for want of effect and, for each from these Age for want of effect and, for each from these categoriescategories,, categories of time from time of effect categories of time from time of effect and sexand sexD – D – Doze equivalent red marrowDoze equivalent red marrow, , in in SivertsSiverts (Sv)(Sv)
MODELS of EXCESS of RISKS D.Pierce, D.Preston, 1996-1999
)expβdθα(d 2EAR
• TTime dependent models ime dependent models of of redundant redundant
rrelative riskelative risk a adapt dapt DOSEDOSE dependence dependence
As linear for As linear for SOLIDSOLID CANCERSCANCERS
As linearly – quadraticAs linearly – quadratic f for or LEUKAEMIALEUKAEMIA
MODELS of MODELS of EXCESSEXCESS of of RISKRISKSS
D.Pierce, D.Preston, 1996-1999D.Pierce, D.Preston, 1996-1999
EPIDEMIOLOGYEPIDEMIOLOGY OF LEUKAEMIAOF LEUKAEMIA
RESUME:The comparative analysis was done for clean-up workers
CWA of 1986 and 1987 by periods of observation of 1987-1991 and 1992-1996.
• The results of the conducted study indicate the increasing of the leukemia risk among CWA of 1986 most vividly during 1987-1991.
• Relative risk was defined at the level of 3,32 (1,08; 10,20), and for 20-59 age group it was 3,45 (1,15; 10,36).
No significant differences were defined in leukemia incidence at survey groups in 1992-1996.
About authorAbout author
Ledoshchuk Boris Alexandrovich born in 1946 in Russia. In 1970 graduated from Blagoveschensk Medical Institute, where also studied in coordinator and at post-graduate course. In 1975 – 1978 worked in the Institute of clinical and experimental medicine of the Academy of Sciences of USSR in Novosibirsk. Took part in scientific epidemiological studies of Far-East and Siberia regions inhabitants. In 1978 – 1985 possessed various positions in medical institutions of Nikolaev region (Ukraine).In 1986 – 1988 worked in the Ministry for Health Care of Ukraine where was responsible for rehabilitation programmer of the population of Chernobyl contaminated area.Since 1988 heads scientific leukemia epidemiology laboratory of the Radiation Medicine Scientific Center. In 1995 – 2000 headed the Medical Department of the Ministry of Atomic Energy.Since 27 April 1986 was involved in clean-up works in the Chernobyl area.One of the leading specialists in the problems of automatic systems of long-term medical monitoring of people damaged in result of Chernobyl accident (State Registry of Ukraine).Author of more than 100 scientific articles and works on the problems of epidemiology, automatic systems of registration and radiation medicine. Prominent participant of international epidemiology projects: AIFIKA, Chernobyl, Leukemia.
B. A. LedoshchukM.D.,Ph.D.
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Radiation Research http://www.radres.org/
Radiation and Health Physics http://www.umich.edu/~radinfo/
Radiation effects Research Foundation www.rerf.or.jp/Radiation effects Research Foundation www.rerf.or.jp/
Radiation effects www.eh.doe.gov/ihp/rerf/Radiation effects www.eh.doe.gov/ihp/rerf/
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Radiation Protection Program (EPA) Radiation Protection Program (EPA) www.epa.gov/radiation/ionize.htm
Research Sources (Radiation, Effects) Research Sources (Radiation, Effects) www.umich.edu/~radinfo/reas.html
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Uranium and Health www.antenna.nl/~wise/uranium/uhr.htmlUranium and Health www.antenna.nl/~wise/uranium/uhr.html
What is epidemiology? www.bmj.comepidem/epid.1.htmlWhat is epidemiology? www.bmj.comepidem/epid.1.html
Ministry of Nuclear of Energy Russia www.minatom.ruMinistry of Nuclear of Energy Russia www.minatom.ru
Epidemiology, Radiation, Chernobyl, Ukraine (ERCU) Epidemiology, Radiation, Chernobyl, Ukraine (ERCU) www.epidemUA.svitonline.com www.epidemUA.svitonline.com
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