Screening Final

8/4/2019 Screening Final

1/25

ROLE OF SCREENING IN PUBLIC HEALTH


2/25

- Process of investigating and identifying unrecognized

diseases or its precursors and disease susceptibility

in individuals through means of simple tests, physical

examinations, laboratory tests or otherprocedures.(2,3)

- Carried out as early detection of disease condition in

individuals who appear healthy and show inapparent

clinical signs of a disease.

Screening


3/25

Screening Methods

- Population or community based screening.

- Selective screening in high-risk individuals

- Opportunistic screening

- Screening of immigrants

- Prenatal and newborn screening


4/25

Disease Spectrum.

screening

Primary

prevention

secondary

prevention

tertiary

prevention

Early

detection

Figure 1: Spectrum of Disease Occurrence.(1)


5/25

Role of Screening

- early detection of risk factors in healthy individuals

and primary prevention to prevent disease

occurrence

- Secondary prevention in individuals whohave started to develop the disease with preclinical

signs and symptoms to prevent the disease from

progressing to the advance stage.

- detection of individuals who are carriers of aparticular disease, to prevent them from spreading

the disease to other individuals.


6/25

Role of Screening (cont.)

-Early detection of risk factors such as genetic

disorders or other deformities from prenatal

screening to educate parents about the high risk in

the unborn.

- Detection of risk factors in a population to plan

control and prevention programs in the aim of

promoting health and improving the quality of life of

individuals

-planning health care resources wisely

-Reducing the disease burden in a population

-Protection of a disease towards the population


7/25

Determining And Interpreting

Measures Used In Screening

SENSITIVITY

Proportion of all cases that are actually called positive by the test

(True positives)

Number of individuals with preclinical disease who test positive X 100%

Number of individuals with preclinical disease

SPECIFICITY

Proportion of all non-cases actually called negative by the test

(True negatives)

Number of individuals without preclinical disease who test negative X 100%

Number of individuals without preclinical disease


8/25

PREDICTIVE VALUE

Main way to measure the feasibility of a screening program

Predictive Value Positive (PVP)

proportion of individuals with a positive test

who have preclinical disease

Number of individuals who test positive and have preclinical disease X 100%

Number of individuals with test positive

Negative Predictive Value (PVN) proportion of individuals without

preclinical disease who test negative

Number of individuals who test negative and do not have preclinical disease X 100%

Number of individuals with test negative


9/25

Calculating Sensitivity, Specificity and Predictive Value Using a

Two-by-Two Table

Yes No Total

Positive a b a + b

Negative c d c + d

Total a + c b + d a + b + c+ d

Disease Status Present

Screening

Test Result


10/25

Based on the 2X2 table on the last slide, the sensitivity, specificity and

predictive values are calculated as below:

Sensitivity = _a_

(a+c)

Specificity = _d_

(b+d)

PVP = _a_

(a+b)

PVP = _d_

(c+d)


11/25

Interpretation A very sensitive case will enable us to catch as many of the cases as

possible, and keep missed cases to a minimum.

A very sensitive test also means a lot of false alarms.

A very specific test will enable us to correctly identify as many of the non-

cases as possible.

Will keep false alarms to a minimum but we will have more missed cases PVP and PVN reflect the underlying prevalence of the disease.

PVP is lesser if there is lower prevalence of cases in the population being

studied.

High PVP is essential for successful screening programme. Indicates a

successful programme because it detects a large number of actual casesamong individuals with positive result.


12/25

By: Cynthia Selviana Sreedevi


13/25

Overview:

A screening test is performed on an asymptomaticperson to detect diseases or a conditions.


14/25

Screening test is used in a variety of way example

being blood pressure is monitored to identifyhypertension, mammography performed to detectbreast cancer, or PSA count to identify prostatecancer and pap smear to detect cervical cancer


15/25

1. To identify the disease in at a early stage thus

making the treatment more effective compared toafter the patient has developed signs andsymptoms.

2. To identify the risk factors that contribute todeveloping a disease therefore allowing to modifythe risk factors to prevent or lessen the disease.


16/25

The pre-clinical phase starts with the start of diseaseprocess and lasts till the signs and symptomsappear, which by then the clinical phase sets inmotion.

The pre-clinical phase of the disease is detectableby screening because patient has not developed anysigns or symptoms.

Once pre-clinical phase is detected, immediate

intervention could take place before the diseaseprogresses to clinical phase which by then screeningis too late.


17/25

1. Rapid results- allowing detection in pre-clinical

stage in diseases.

2. Accessible with minimum cost.

3. Safe to administer.4. Simple

5. Acceptable to target group


18/25

CURRENT SCREENING TESTS USED ANDITS USEFULLNESS


19/25

Screening Tests Used

- blood pressure monitoring for hypertension

- mammography for breast cancer detection

- Rapid HIV tests for HIV detection

- Many others (PKU Tests, Blood Glucose Tests, etc

- Pap smears for cervical cancer


20/25

Blood Pressure Monitoring

-Hypertension is a high risk factor for cardiovascular diseases which in one of the leadingcause of diseases worldwide. Can be contributed by various factors such as obesity.

-Blood pressure can be monitored using a blood pressure monitor/

sphygmomanometer and is measured in mimilmeters of mercury.

- Good diagnosis is made by taking two or more blood pressure readings while the

individual is in a seated position.

-If hypertension is confirmed, subsequent investigation followed by conveyance ofpreventive and corrective measures to bring down the blood pressure

Table 1: Classification of Hypertension (13)


21/25

Mammography

-Breast cancer is the top leading cause of cancers among women in most countriesaround the world including Malaysia

-Mammography is an imaging procedure which uses low energy X-rays for imaging

breast tissue.

-It is used to visualize presence of masses or calcifications which could indicate breastcancer. If these signs are present, further diagnosis is done using a diagnostic

mammography

-National Cancer Institute recommends women above 40 or those below 40 with high

risk, to go for mammograms every 1-2 years.


22/25

Rapid HIV Tests

- Test is used to detect HIV which is one of the fastest growing epidemics in Malaysiaamong the East Asia and the Pacific Region.

- A screening procedure that is relatively accessible and quick and takes 20 minutes.

- Uses individuals blood from vein/ finger prick or other oral fluid to detect presence of

HIV antibodies.

-If tested positive, further confirmatory diagnostic tests are used.

- The tests have similar accuracy levels to traditional EIA screening tests


23/25

Pap Smears (Cytology Tests)

- Cervical Cancer is the second most common cancers in women in Malaysia. Mostlycaused by Human Papillomavirus

- Can be easily prevented through regular screening via pap smears.

- The screening is done by collecting cells from the cervix and placing in on a slide which

is sent to the laboratory for diagnosis to determine abnormality and presence of pre-cancerous cells.

-Presence of abnormal smear could be due to inflammations, or abnormal cells (cervical

dysplasia)

-A reliable test that can be done to prevent abnormal or precancerous cells frombecoming cervical cancer


24/25

Other Screening Tests

-blood glucose tests

-Lipoprotein profile tests

-Infant screening ( PKU testing)

- chest X rays


25/25

References

1. Braveman P, Tarimo E. Screening in Primary Health Care. England: World Health Organization; 19942. Cevical Cancer Screening [Internet]. Center for Disease Control and Prevention; 2010 Sept 2 [updated 2011 Aug 19; cited 2011

Sept 17].

Available from: http://www.cdc.gov/cancer/cervical/basic_info/screening.htm

3. Donaldson LJ, Donaldson RJ. Essential Public Health. 2nd Ed. UK: Radcliff Publishing; 2002.

4. Friis RH, Sellers, TA. Epidemiology for Public Health Practice. London: Jones and Bartlett Publishers; 2008.

5. Gordis L. Epidemiology. Philadelphia: Saunders Elsevier; 2009.

6. Guidelines for the management of hypertension in patients with diabetes mellitus [Internet]. World Health Organization; 2006

[cited 2011 Sept 17]

Available from: http://www.emro.who.int/dsaf/dsa700.pdf7. HIV Testing Basics for Consumers [Internet]. Center for Disease Control and Prevention; 2010 Apr 9 [updated 2010 Apr 9;

cited 2011 Sept 17].

Available from: http://www.cdc.gov/hiv/topics/testing/resources/qa/index.htm

8. Khan AR, Narayan KA. Lecture Notes on Epidemiology. Malaysia: Aimst University; 2007.

9. Mammography [Internet]. World Health Organization; 2011 [cited 2011 Sept 17].

Available from: http://www.who.int/diagnostic_imaging/imaging_modalities/dim_mammography/en/

10. Mammograms [Internet]. National Cancer Institute, 2010 Sept 22 [cited 2011 Sept 17].

Available from: http://www.cancer.gov/cancertopics/factsheet/Detection/mammograms

11. Rapid HIV Testing [Internet]. Center for Disease Control and Prevention; 2009 Jul 24 [updated 2009 Jul 24; cited 2011 Sept 17].

Available from: http://www.cdc.gov/hiv/topics/testing/resources/qa/index.htm

12. Screening [Internet]. Center for Disease Control and Prevention; 2010 Aug 31 [updated 2011 Aug 10; cited 2011 Sept 17].

Available from: http://www.cdc.gov/cancer/breast/basic_info/screening.htm

13. The Economics of Cervical Cancer [Internet]. Malaysian Oncological Society; 2009 [cited 2011 Sept 17].

Available from: http://www.malaysiaoncology.org/article.php?aid=667

14. WHO/ISH Hypertension Guidelines [Internet]. World Health Organization; 2011 [cited 2011 Sept 17]

Available from: http://www.who.int/cardiovascular_diseases/guidelines/hypertension/en/index.html
http://www.cdc.gov/cancer/cervical/basic_info/screening.htmhttp://www.emro.who.int/dsaf/dsa700.pdfhttp://www.cdc.gov/hiv/topics/testing/resources/qa/index.htmhttp://www.who.int/diagnostic_imaging/imaging_modalities/dim_mammography/en/http://www.cancer.gov/cancertopics/factsheet/Detection/mammogramshttp://www.cdc.gov/hiv/topics/testing/resources/qa/index.htmhttp://www.cdc.gov/cancer/breast/basic_info/screening.htmhttp://www.malaysiaoncology.org/article.php?aid=667http://www.who.int/cardiovascular_diseases/guidelines/hypertension/en/index.htmlhttp://www.who.int/cardiovascular_diseases/guidelines/hypertension/en/index.htmlhttp://www.malaysiaoncology.org/article.php?aid=667http://www.cdc.gov/cancer/breast/basic_info/screening.htmhttp://www.cdc.gov/hiv/topics/testing/resources/qa/index.htmhttp://www.cancer.gov/cancertopics/factsheet/Detection/mammogramshttp://www.who.int/diagnostic_imaging/imaging_modalities/dim_mammography/en/http://www.who.int/diagnostic_imaging/imaging_modalities/dim_mammography/en/http://www.cdc.gov/hiv/topics/testing/resources/qa/index.htmhttp://www.emro.who.int/dsaf/dsa700.pdfhttp://www.cdc.gov/cancer/cervical/basic_info/screening.htm

Screening Final

Documents

Transcript of Screening Final