By
Basem Salama Eldeek
MSc,MD,MHPE
Associate prof of community medicine
Faculty of medicine king Abdulaziz university,KSA
...
Acknowledgement
•  The study of the factors affecting cancer, as a way to
infer possible trends and causes.
•  The study of cancer epidemi...
•  This area of study must contend with
problems of
•  lead time bias
•  length time bias.
 
•  Lead time bias is the concept that early
diagnosis may artificially inflate the
survival statistics of a cancer, with...
•  Length bias is the concept that slower
growing, more indolent tumors are more likely to be
diagnosed by screening tests...
•  A similar epidemiological concern is overdiagnosis,
the tendency of screening tests to diagnose diseases
that may not a...
 
•  Observational epidemiological studies that show
associations between risk factors and specific
cancers mostly serve t...
Robert A. Weinberg, "If we lived long enough, sooner or later we all
would get cancer."[10]
•  Over a third of cancer deat...
 
•  Men with cancer are twice as likely as women to have a
modifiable risk factor .[11]
•  lifestyle and environmental fa...
 	
  
•  Every year, at least 200,000 people die worldwide from
cancer related to their workplace.[12]
•  Millions of work...
•  The Saudi Cancer Registry (SCR) of Saudi Arabia is
a population-based registry established in 1992
under the the Minist...
Objec'ves:	
  
•  The primary goal of the SCR is to define the
population-based incidence of cancer in Saudi
Arabia. Addit...
Saudi Cancer Registry has eleven reports .
§  1994 Summary Report,
§  1994-1996 Incidence Report,
§  1997-1998 Incidenc...
Cancer report Total reporting
cancer cases
Estimated
population at
K S A
Absolute
incidence
1994-­‐1996	
   23092	
   1408...
20	
  
25	
  
30	
  
35	
  
40	
  
45	
  
50	
  
55	
  
60	
  
65	
  
70	
  
75	
  
20	
  
25	
  
30	
  
35	
  
40	
  
45	
  
50	
  
55	
  
60	
  
65	
  
70	
  
75	
  
Absolute	
  incidence	
  	
  
absolute...
94	
   95	
   96	
   97	
   98	
   99	
   20	
   01	
   02	
   03	
   04	
   05	
   06	
   07	
  
Thyroid	
  
C	
  73	
  
...
94	
   95	
   96	
   97	
   98	
   99	
   20	
   01	
   02	
   03	
   04	
   05	
   06	
   07	
  
Leukemi
a	
  
C92,94	
  ...
94	
   95	
   96	
   97	
   98	
   99	
   20	
   01	
   02	
   03	
   04	
   05	
   06	
   07	
  
Breast	
  C50	
  
13.4	
...
§  The total number of cancer incident cases reported to
the SCR was 12,309.
§  Overall cancer was slightly more among w...
•  11,651 cases were analyzed, of which
9,124 (78.3%) were Saudis and 2,527
(21.7%) were Non-Saudis.
Among the Saudis
•  4...
Confirmation of Diagnosis of
malignancy
•  Histologically in 86.2% of the cases.
•  Haematological & cytologically in 8% o...
Age adjusted rate (ASR) of all cancers
among Saudi Population
47	
  
48	
  
49	
  
50	
  
51	
  
52	
  
53	
  
total	
   Men	
   Women	
  
CIR	
  
CIR per
100,000
	
  
Total 52.3%
Men ...
Age adjusted rate (ASR) of all cancers
among Saudi Population
77	
  
78	
  
79	
  
80	
  
81	
  
82	
  
83	
  
84	
  
85	
...
The age-specific incidence
rate (AIR) increased with
age for gender.
After the age of 64 years,
the increase was nearly on...
§  Riyadh Region
108.5/100,000
§  Tabuk Region
105.0/100,000
§  Eastern Region
104.4/100,000
§  Makkah Region
89.3/100...
Percentage	
  distribu'on	
  of	
  most	
  frequent	
  type	
  of	
  
cancer	
  by	
  gender	
  2007	
  age	
  (0-­‐14	
  ...
Percentage	
  distribu'on	
  of	
  most	
  frequent	
  type	
  of	
  
cancer	
  by	
  gender(	
  above	
  14	
  years)	
  ...
Percentage	
  distribu'on	
  of	
  most	
  frequent	
  type	
  
of	
  cancer	
  by	
  age	
  and	
  	
  gender	
  2007	
  ...
Percentage	
  distribu'on	
  of	
  most	
  frequent	
  type	
  
of	
  cancer	
  by	
  gender	
  2007	
  	
  
Percentage	
  distribu'on	
  of	
  most	
  frequent	
  type	
  of	
  
cancer	
  by	
  gender	
  2007	
  age	
  (15-­‐29	
 ...
Percentage	
  distribu'on	
  of	
  most	
  frequent	
  type	
  of	
  
cancer	
  by	
  gender	
  2007	
  age	
  (30-­‐44	
 ...
Percentage	
  distribu'on	
  of	
  most	
  frequent	
  type	
  of	
  
cancer	
  by	
  gender	
  2007	
  age	
  (45-­‐59	
 ...
Percentage	
  distribu'on	
  of	
  most	
  frequent	
  type	
  of	
  
cancer	
  by	
  gender	
  2007	
  age	
  (60-­‐74	
 ...
Percentage	
  distribu'on	
  of	
  most	
  frequent	
  type	
  of	
  
cancer	
  by	
  gender	
  2007	
  age	
  (75+year)	
...
Males	
  	
  
Females	
  	
  
Specific cancer common in female
Males and 6.6 / 100,000 females
Preventive oncology
Summary Of Primary Preventive
Actions
Prospects seem bright for ultimately preventing many
cancers. There is already much ...
5.	
  Restrict use of drugs that are known/suspected to be
carcinogenic.
6. Prudent use of diagnostic x-rays.
7. Avoid exc...
5.	
  Restrict use of drugs that are known/suspected to be
carcinogenic.
6. Prudent use of diagnostic x-rays.
7. Avoid exc...
Screening for cancer
SCREENING AND 2 RY PREVENTION
•  By means of early detection followed by
definitive treatment.
•  Screening is one compone...
Natural history of a disease over time, including the pre-
clinical stage in which a screening test can detect the
presenc...
The clinical decision-making is
based on probability.
Probability of breast cancer (percent)
0 20 40 60 80 100
Before
mamm...
Bias in Screening
lead-time bias	
  	
  DNAdamage
Cancerbegins
Cancer
firstscreendetectable
Lead
time
Death
Patient diagno...
Advanced Uses of Screening Tests
-To Determine the probability that a disease is
present’
-To assess the severity of an il...
Evaluation of a screening Test.
Evaluation of a Diagnostic Test.
Truth (gold standard)
Test results
(Screening
test)
No diseaseDisease
b
False-positive
No...
Evaluation of a Diagnostic Test.
Sensitivity and Specificity
Sensitivity and specificity are descriptors of
the accuracy o...
Evaluation of a Diagnostic Test.
Sensitivity and Specificity
Specificity of a test is defined as the percentage
of persons...
Evaluation of a Diagnostic Test.
Total
Surgical biopsy
FNA results
No cancerCancer
228
False-
positive
14
True
positive
Po...
Positive and Negative Predictive Value
Two measures concerning the estimation of the
probability of the presence or absenc...
Positive and Negative Predictive
Value
The PV- is defined as the percentage of who do
not have the disease of interest to ...
Likelihood Ratios
(LR)
Likelihood Ratios LR + Likelihood Ratios LR -
Likelihood Ratios
An LR+ of 1, indicates a test of no value in sorting
out persons with and without disease.
The larger th...
1.  	
  WHO	
  Disease	
  and	
  injury	
  country	
  esHmates".	
  World	
  Health	
  OrganizaHon.	
  2009.	
  
hMp://www...
References	
  
9-­‐Saudi	
  cancer	
  register	
  incidence	
  report	
  ,2003.	
  
10-­‐Saudi	
  cancer	
  register	
  in...
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]
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Dr. basem aldeek some%final epidemiological aspects about cancer in king saudi[1]1 [autosaved]

  1. 1. By Basem Salama Eldeek MSc,MD,MHPE Associate prof of community medicine Faculty of medicine king Abdulaziz university,KSA And mansoura university ,Egypt.    
  2. 2. Acknowledgement
  3. 3. •  The study of the factors affecting cancer, as a way to infer possible trends and causes. •  The study of cancer epidemiology uses epidemiological methods to find the cause of cancer and to identify and develop improved treatments.
  4. 4. •  This area of study must contend with problems of •  lead time bias •  length time bias.
  5. 5.   •  Lead time bias is the concept that early diagnosis may artificially inflate the survival statistics of a cancer, without really improving the natural history of the disease.
  6. 6. •  Length bias is the concept that slower growing, more indolent tumors are more likely to be diagnosed by screening tests, but improvements in diagnosing more cases of indolent cancer may not translate into better patient outcomes after the implementation of screening programs.
  7. 7. •  A similar epidemiological concern is overdiagnosis, the tendency of screening tests to diagnose diseases that may not actually impact the patient's longevity. This problem especially applies to prostate cancer and PSA screening. •  Some cancer researchers have argued that negative cancer clinical trials lack sufficient statistical power to discover a benefit to treatment.
  8. 8.   •  Observational epidemiological studies that show associations between risk factors and specific cancers mostly serve to generate hypotheses •  Randomized controlled trials then test whether hypotheses generated by epidemiological studies and laboratory research actually result in reduced cancer incidence and mortality. •  Programmatic trials.
  9. 9. Robert A. Weinberg, "If we lived long enough, sooner or later we all would get cancer."[10] •  Over a third of cancer deaths worldwide are due to potentially modifiable risk factors §  Tobacco smoking, lung cancer, mouth, and throat cancer; §  Drinking alcohol, oral, esophageal, breast, and other cancers; §  A diet low in fruit and vegetables, §  Physical inactivity, colon, breast, §  Obesity, is associated with colon, breast, endometrial §  Sexual transmission of human papillomavirus, which causes cervical cancer &anal cancer.
  10. 10.   •  Men with cancer are twice as likely as women to have a modifiable risk factor .[11] •  lifestyle and environmental factors known to affect cancer risk . •  use of exogenous hormones (e.g., hormone replacement therapy causes breast cancer) •  exposure to ionizing radiation and ultraviolet radiation, and certain occupational and chemical exposures.
  11. 11.     •  Every year, at least 200,000 people die worldwide from cancer related to their workplace.[12] •  Millions of workers run the risk of developing cancers such as pleural and peritoneal mesothelioma from inhaling asbestos fibers, or leukemia from exposure to benzene .[12] •  It is estimated that approximately 20,000 cancer deaths and 40,000 new cases of cancer each year in the U.S. are attributable to occupation.[13]
  12. 12. •  The Saudi Cancer Registry (SCR) of Saudi Arabia is a population-based registry established in 1992 under the the Ministry of Health (MOH) by the order of His Excellency the Minister of Health. •  The SCR commenced reporting cancer cases from 01 January 1994.
  13. 13. Objec'ves:   •  The primary goal of the SCR is to define the population-based incidence of cancer in Saudi Arabia. Additional objectives include programs for early detection and cancer screening, as well as cancer research projects.
  14. 14. Saudi Cancer Registry has eleven reports . §  1994 Summary Report, §  1994-1996 Incidence Report, §  1997-1998 Incidence Report, §  1999-2000 Incidence Report, §  2001 Incidence Report, §  2002, 2003, 2004, 2005, 2006, §  2007and Incidence Reports.  
  15. 15. Cancer report Total reporting cancer cases Estimated population at K S A Absolute incidence 1994-­‐1996   23092   14089156   54.36      per  1000000   1997-­‐1998   14529   15121791   48.03      per  1000000   1999-­‐2000   14856   15588805   47.06    per  1000000   2001   5616   16056470   34.72    per  1000000   2002   5876   15612781   37.63    per  1000000   2003   8840   16109198   54.78    per  1000000   2004   9381   16527340   56.76  per  1000000   2005   10513   16945484   62.47  per  1000000   2006   11040   17270181   63.92  per  1000000   2007   12,309   17493364   70.63  per  1000000  
  16. 16. 20   25   30   35   40   45   50   55   60   65   70   75  
  17. 17. 20   25   30   35   40   45   50   55   60   65   70   75   Absolute  incidence     absolute  incidence    
  18. 18. 94   95   96   97   98   99   20   01   02   03   04   05   06   07   Thyroid   C  73   5.5   5.3   4.6   5   5.7   5.4   4.8   4.6   4.7   6.1   5.7   6.4   6.5   6.6   Colon     C18   2.2   2.7   2.6   2.2   2.2   2.9   2.6   3.4   3.1   4.2   4.3   4.3   5.3   4.8   NHL   C82,85, 96   4.3   4.2   4.1   4   5   4.3   4.1   4.4   4.4   5   5   5.3   4.8   5.1  
  19. 19. 94   95   96   97   98   99   20   01   02   03   04   05   06   07   Leukemi a   C92,94   1.8   1.8   1.7   1.6   1.7   1.6   1.7   1.8   1.8   1.6   1.9   1.6   2   1.5     Hodgkin   C81   1.4   1.3   1   1.1   1.3   1.2   1.2   1.1   1   1.5   1.4   1.3   1.6   1.6     stomach   C16   2.4   2.4   2.1   1.8   2   1.9   1.6   1.7   1.8   1.8   1.7   1.7   2.7   2.5    liver   C22   3.9   3.1   3.3   2.9   3.8   2.7   3.2   2.7   2.8   3.3   2.9   3.1   3.1   2.6  
  20. 20. 94   95   96   97   98   99   20   01   02   03   04   05   06   07   Breast  C50   13.4   13   13.4   13.3   14.3   12.6   13.7   12.1   13.9   14.6   16.5   18.7   18.1   21.6   Corpus  uteri  C54   2.1   1.4   1.4   1.6   2   1.6   2.5   2.1   2.2   2.8   2.9   3.6   3.6   4   Corpus  cervix  C53   2.4   2.2   2.5   2.3   2.9   2   1.9   2   1.8   1.9   2   2.1   1.6   1.9   Ovary  C56   2.9   3   2.7   3.1   3.1   2.2   2.2   2.4   2.3   2.5   2.4   2.9   3   2.6  
  21. 21. §  The total number of cancer incident cases reported to the SCR was 12,309. §  Overall cancer was slightly more among women than men. §  Cancers affected 5,982 (48.6%) males and 6,321 (51.4%) females with a male to female ratio of 95:100. §  9,347 cases were reported among Saudis, §  2,590 among Non-Saudis.
  22. 22. •  11,651 cases were analyzed, of which 9,124 (78.3%) were Saudis and 2,527 (21.7%) were Non-Saudis. Among the Saudis •  4,351 (47.7%) were male •  4,773 (52.3%) were female. •  The male to female ratio •  was 91:100. 47%   53%   proportion Males   Female  
  23. 23. Confirmation of Diagnosis of malignancy •  Histologically in 86.2% of the cases. •  Haematological & cytologically in 8% of cases. •  Clinically confirmed cases were 0.3%. •  Radiologically confirmed cases were 2%. •  Cases confirmed by Death Certificate Only were 2.7% . •  The method of diagnosis was unknown for 0.8% of the cases.
  24. 24. Age adjusted rate (ASR) of all cancers among Saudi Population
  25. 25. 47   48   49   50   51   52   53   total   Men   Women   CIR   CIR per 100,000   Total 52.3% Men 49.4 % women 51.5%
  26. 26. Age adjusted rate (ASR) of all cancers among Saudi Population 77   78   79   80   81   82   83   84   85   Total   Men   Women   ASR   ASR per 100,000   Total 82.1 Men 80 women 84.2
  27. 27. The age-specific incidence rate (AIR) increased with age for gender. After the age of 64 years, the increase was nearly one and one half fold for males compared to females. The median age at diagnosis is was 59 years for men and 50 years for women
  28. 28. §  Riyadh Region 108.5/100,000 §  Tabuk Region 105.0/100,000 §  Eastern Region 104.4/100,000 §  Makkah Region 89.3/100,000 §  Madinah Region 73.8/100,000.   0   20   40   60   80   100   120   ASR   ASR  
  29. 29. Percentage  distribu'on  of  most  frequent  type  of   cancer  by  gender  2007  age  (0-­‐14  year)Saudi  children    
  30. 30. Percentage  distribu'on  of  most  frequent  type  of   cancer  by  gender(  above  14  years)  2007  Saudi  Adult      
  31. 31. Percentage  distribu'on  of  most  frequent  type   of  cancer  by  age  and    gender  2007    
  32. 32. Percentage  distribu'on  of  most  frequent  type   of  cancer  by  gender  2007    
  33. 33. Percentage  distribu'on  of  most  frequent  type  of   cancer  by  gender  2007  age  (15-­‐29  year)  
  34. 34. Percentage  distribu'on  of  most  frequent  type  of   cancer  by  gender  2007  age  (30-­‐44  year)  
  35. 35. Percentage  distribu'on  of  most  frequent  type  of   cancer  by  gender  2007  age  (45-­‐59  year)  
  36. 36. Percentage  distribu'on  of  most  frequent  type  of   cancer  by  gender  2007  age  (60-­‐74  year)  
  37. 37. Percentage  distribu'on  of  most  frequent  type  of   cancer  by  gender  2007  age  (75+year)  
  38. 38. Males    
  39. 39. Females    
  40. 40. Specific cancer common in female
  41. 41. Males and 6.6 / 100,000 females
  42. 42. Preventive oncology
  43. 43. Summary Of Primary Preventive Actions Prospects seem bright for ultimately preventing many cancers. There is already much that can be done: 1. Quit smoking and use of tobacco in any from, and encourage all nonusers not to start (especially the young). 2. Stop alcohol. 3. Control exposures to known carcinogens in the workplace. 4. Reduce exposures outside the workplace to known carcinogens such as arsenic, chromium, nickel, vinyl chloride, and asbestos.
  44. 44. 5.  Restrict use of drugs that are known/suspected to be carcinogenic. 6. Prudent use of diagnostic x-rays. 7. Avoid excess exposure to sunlight, especially for fair skinned persons, and encourage use of protective creams and sunscreen. 8. Avoid giving estrogens to pregnant women. Use the lowest dose necessary and include a progestin in the regimen. Summary Of Primary Preventive Actions
  45. 45. 5.  Restrict use of drugs that are known/suspected to be carcinogenic. 6. Prudent use of diagnostic x-rays. 7. Avoid excess exposure to sunlight, especially for fair skinned persons, and encourage use of protective creams and sunscreen. 8. Avoid giving estrogens to pregnant women. Use the lowest dose necessary and include a progestin in the regimen. Summary Of Primary Preventive Actions
  46. 46. Screening for cancer
  47. 47. SCREENING AND 2 RY PREVENTION •  By means of early detection followed by definitive treatment. •  Screening is one component of early detection Secondary prevention can be achieved only if there is a stage of that cancer that is amenable to cure, and if there are means of detecting the cancer at that stage.
  48. 48. Natural history of a disease over time, including the pre- clinical stage in which a screening test can detect the presence of disease. A screening test can identify diseased individuals before Detection by routine diagnosis (Occurance of symptoms). Treatment at the time of detection by screening, as opposed to the time of routine diagnosis, results in an improved chance of survival. Biologic onset of disease Disease detectable by screening Detection by Screening test Detectable by routine methods Death treatment
  49. 49. The clinical decision-making is based on probability. Probability of breast cancer (percent) 0 20 40 60 80 100 Before mammogram After positive mammogram After positive FNA results 0.3 13 64 Diagnostic test (screening test) is to move the estimated probability of the presence of a disease toward either end of probability scale, thereby providing information that will alter subsequent diagnostic or treatment plans.
  50. 50. Bias in Screening lead-time bias    DNAdamage Cancerbegins Cancer firstscreendetectable Lead time Death Patient diagnosed from clinical symptoms Apparent survival Apparent survivalPatient diagnosed by screening Lead time Lead time bias is an increase in survival as measured From detection of disease to death, without lengthening of life.
  51. 51. Advanced Uses of Screening Tests -To Determine the probability that a disease is present’ -To assess the severity of an illness’ -To predict the disease outcome’ -To monitor response to therapy’ -To estimate the probability of an outcome.
  52. 52. Evaluation of a screening Test.
  53. 53. Evaluation of a Diagnostic Test. Truth (gold standard) Test results (Screening test) No diseaseDisease b False-positive Non diseased+ positive test a True positive Disease present +test positive Positive d True negative Non diseased with negative test c False- negative Have the disease with negative test results Negative
  54. 54. Evaluation of a Diagnostic Test. Sensitivity and Specificity Sensitivity and specificity are descriptors of the accuracy of a test. The sensitivity of a test is defined as the percentage of persons with the disease of interest who have positive test results: few false positive Sensitivity = X 100 = a/a + c X100 = 14/14+1 X100 = 93 % True positives True positive+ false negatives
  55. 55. Evaluation of a Diagnostic Test. Sensitivity and Specificity Specificity of a test is defined as the percentage of persons without the disease of interest who have negative test results It is the ability of the test to rule out the non- diseased few false negative Specificity = X 100 = d /d + b X 100 = 91/91+8 X100 = 92 % True negatives True negatives + false-positives
  56. 56. Evaluation of a Diagnostic Test. Total Surgical biopsy FNA results No cancerCancer 228 False- positive 14 True positive Positive 9291 True negative 1 False- negative Negative 1149915Total Sensitivity = 14/14+1 X100 = 93 % Specificity = 91/91+8 X100 = 92 %
  57. 57. Positive and Negative Predictive Value Two measures concerning the estimation of the probability of the presence or absence of disease are the positive predictive value (PV+) and the negative predictive value (PV-). The PV+ is defined as the percentage of who actually have the disease of interest to persons with positive test results (allow us to estimate how likely it is the disease of interest is present if the test is positive). PV+= X 100 = a/a + b X100 = 14/ 14+8 X100 = 64 % True positives True positives +false positives
  58. 58. Positive and Negative Predictive Value The PV- is defined as the percentage of who do not have the disease of interest to persons with negative test results : PV- = X 100 = d/ d + c X100 = 91 /91+1 X100 = 99 % True negatives True negatives + false negatives
  59. 59. Likelihood Ratios (LR) Likelihood Ratios LR + Likelihood Ratios LR -
  60. 60. Likelihood Ratios An LR+ of 1, indicates a test of no value in sorting out persons with and without disease. The larger the LR+more than 1 , the stronger the association between having a positive test result and having the disease. LR+ of more than 10 is an indication of a test of high diagnostic value. The smaller the LR- value, the better the diagnostic value of the test. An LR- of 0.1 or less is an indication of a good diagnostic test.
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