Descriptive Epidemiology Lecture 4.1 PDF

Descriptive Epidemiology Dr Muhammad Ahmed Alshyyab Lecture 1 Chapter 4 Lecture objectives To understand What is descriptive epidemiology? To identify and discuss all of the descriptive epidemiology data sources; Case series, Surveillance systems, Nationa...

Descriptive Epidemiology Dr Muhammad Ahmed Alshyyab Lecture 1 Chapter 4 Lecture objectives To understand What is descriptive epidemiology? To identify and discuss all of the descriptive epidemiology data sources; Case series, Surveillance systems, National health surveys and vital record systems Insatiable Curiosity “I Keep six honest serving-men: (They taught me all I knew) Their names are What and Where and When And How and Why and Who.” Rudyard Kipling (1865–1936) What is descriptive epidemiology? Descriptive epidemiology is to describe disease occurrence and generate hypotheses and ideas about cause. According to the epidemiologic variables of person, place, and time. Analytic epidemiology: starts with specific hypotheses about cause and then designs its studies to address these specific hypotheses.  Descriptive – Analytic Spectrum Descriptive Analytic Hypothesis Hypothesis Generating Testing Standing data Ad hoc data sources collection It should be noted that there is no firm demarcation between descriptive epidemiology and analytic epidemiology: all epidemiologic studies serve to advance knowledge of disease causation and prevention, and many studies serve both descriptive and analytic purposes. Descriptive epidemiology data sources 1. Case series 2. surveillance systems 3. Vital records and nation health surveys. Case series Case series describe the medical history and clinical manifestations of a small number of individuals with a particular disease or syndrome. ‘‘Denominator data’’ is absent from case series. Therefore, case series cannot calculate incidence or prevalence. no referent or ‘‘control’’ series is present. No causal conclusion in case series Observations derived from cases series often signal an emerging problem and help clarify hypotheses for further investigation. Example Acquired immune deficiency syndrome (case series) In 1981, local clinicians and the Epidemic Intelligence Service Officer stationed at the Los Angeles County Department of Public Health prepared and submitted a report of five cases of Pneumocystis pneumonia in previously healthy young men (CDC, 1981, 2001). Before publication, editorial staff at the CDC sent the report to experts in parasitic and sexually transmitted diseases who noted that the case histories suggested that they were dealing with cellular- immune dysfunction disease acquired through sexual contact. At about the same time, the sole distributor of the antifungal drug (pentamidine) used to treat Pneumocystis pneumonia in the United States began receiving multiple requests for the medicine from physicians throughout the country. The affected individuals were, again, young men. In June 1981, CDC developed an investigative team to develop a case definition and identify risk factors for this new syndrome. One of keys clues leading to discovery of AIDS: Case Series 5 cases of Pneumocystis pneumonia in previously healthy young men Pharmacist noticed unusual requests for antifungal drug pentamidine STD experts noted cellular immune dysfunction Public health surveillance Surveillance systems Epidemiologic surveillance systems are structures set up to routinely collect and analyse data for specific types of health outcomes. Epidemiologic surveillance systems may be either active or passive in nature. Used for 1. characterizing the patterns of disease 2. detecting outbreaks 3. further investigation 4. research 5. disease control programs 6. Setting public health priorities 7. evaluating health programs Surveillance systems cycle Active surveillance systems Require actively seeking- out cases in defined populations, and thus requires the use of specially trained personnel to retrieve and review health care and laboratory records to discover and confirm cases. Active surveillance Actively sought out Example on active surveillance systems The Surveillance, Epidemiology and End Results (SEER) program of the National Cancer Institute is an active surveillance system that functions as the primary source of cancer statistics in the United States. SEER registries routinely collect data on patient demographics, primary tumour site, tumour morphology, stage at diagnosis, first course of treatment, and patient survival. Data from the Census Bureau are used as denominator information to calculate cancer rates within the capturement area of each of the SEER registries. SEER then compiles cancer statistics from each region to estimate cancer incidence for the entire country.  Example Endometrial cancer (active surveillance) SEER data – active surveillance of cancer occurrence Increases in uterine cancer 1969 - 73 Parallel increases in the use of estrogen prescribed for symptoms of menopause and osteoporosis Analytic epi and animal studies corroborated descriptive findings