Public Health & Preventive Medicine: 12 practice questions
Public Health & Preventive Medicine is 10% of the Emirates Medical Residency Entrance Examination, across 22 blueprint topics. Try twelve questions from Axiota's EMREE pack, which has 235 cards on this section.
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Prevention & Health Maintenance · Infectious Diseases II — Choosing the Drug
What minimum vaccination coverage rate is required to establish herd immunity against measles?
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Because it is extraordinarily transmissible — nine out of ten people who are not immune and share living space with an infected person will be infected. More than 95% of the community must be vaccinated in order to achieve herd immunity. A coverage rate that would control most infections leaves measles circulating.
Prevention & Health Maintenance · Psychiatry II — Obsessions, Trauma, Attention, Sleep and Self-Harm
In the United States, what rank does suicide hold as a leading cause of death among adolescents aged 10 to 14?
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Because of what sits behind it at that age. Suicide is the second leading cause of death for adolescents between the ages of 10 and 14 and the third leading cause among older adolescents in the United States, and in Australia it is second only to traffic collisions for those aged 15 to 25. Community support programmes offering safe spaces to express emotions are part of the response, not an optional extra.
Diagnoses & Investigations · Public Health — Prevention, Environment and Outbreaks
What body mass index (BMI) threshold defines obesity in standard adult classifications?
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Obese, managed first by diet and activity. People are classified as obese when their body mass index is over 30 kg/m2; the range 25-30 is defined as overweight. Changes to diet as well as exercising are the main treatments recommended by health professionals. Some East Asian countries use lower thresholds, so the cut-off is population-specific.
Diagnoses & Investigations · Test Statistics, Screening and Epidemiological Measures
In a cohort of 50 diseased individuals, 45 test positive. Among 150 non-diseased individuals, 30 test positive. What is the sensitivity?
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90%. Sensitivity is TP / (TP + FN) = 45 / 50 = 0.90. The 30 false positives belong to the specificity calculation, not this one: specificity is TN / (TN + FP) = 120 / 150 = 80%. The commonest error is dividing by the total who tested positive (45/75), which gives positive predictive value instead.
Prevention & Health Maintenance · Public Health — Prevention, Environment and Outbreaks
Which malignancy is the leading cause of cancer-related death among women worldwide?
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Lung cancer — which makes smoking cessation the highest-value conversation. Lung cancer has overtaken all other types of cancer as the leading cause of cancer related death in women, followed by breast cancer. While smoking is the major cause, among nonsmoking women the risk of developing lung cancer is three times greater than among nonsmoking men, so a negative smoking history does not dismiss the symptom.
Fundamental Scientific Concepts · Test Statistics, Screening and Epidemiological Measures
Which statistical measure directly influences positive and negative predictive values between different clinical populations?
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Prevalence. Positive and negative predictive values, but not sensitivity or specificity, are values influenced by the prevalence of disease in the population being tested. Sensitivity and specificity are properties of the test; predictive value is a property of the test *and* the population. The same positive result therefore means something different in a screening clinic than in a referral centre.
Prevention & Health Maintenance · Public Health — Prevention, Environment and Outbreaks
What term describes the indirect protection from infectious disease that occurs when a large proportion of a population is immune?
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Herd immunity. It is a form of indirect protection that applies only to contagious diseases: when a large proportion of the population have been immunized, this prevents the illness from spreading significantly, including to unimmunized people. Some individuals either cannot develop immunity after vaccination or for medical reasons cannot be vaccinated — they are precisely who the threshold protects.
Prevention & Health Maintenance · Test Statistics, Screening and Epidemiological Measures
Which set of guidelines outlines the principles required before implementing a screening programme?
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The Wilson and Jungner criteria, from the 1968 WHO guidelines: the condition should be an important health problem, there should be a treatment for the condition, and the test should be acceptable to the population, among ten principles. The pivotal one is treatability — detecting a disease earlier is worthless if nothing can be done sooner about it.
Diagnoses & Investigations · Public Health — Prevention, Environment and Outbreaks
Which diagnostic investigation is used to confirm a diagnosis of obstructive sleep apnoea?
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A sleep study. A bed partner or family member may observe a person snoring or appear to stop breathing, gasp, or choke while sleeping, and the syndrome is named when this is associated with daytime symptoms such as excessive sleepiness and decreased cognitive function. The history raises it; polysomnography measures it.
Fundamental Scientific Concepts · Test Statistics, Screening and Epidemiological Measures
Which bias creates an apparent increase in survival time simply by diagnosing a condition earlier without altering the time of death?
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Lead time bias. If screening works it must introduce a lead time, so statistics of survival time since diagnosis tend to increase with screening because of the lead time introduced, even when screening offers no benefits. The clock started earlier without the endpoint moving — which is why screening programmes are judged on mortality, not on survival from diagnosis.
Non-pharmacologic Management · Public Health — Prevention, Environment and Outbreaks
Which multidisciplinary assessment process is established to improve health outcomes in frail older inpatients?
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Comprehensive geriatric assessment. The various members of the geriatric medicine multidisciplinary team assess different domains, and the use of CGA improves the medical outcomes for older people. The limiting factor is availability: there is a relative lack of geriatricians with the training to contribute, so many who would benefit do not receive one.
Fundamental Scientific Concepts · Test Statistics, Screening and Epidemiological Measures
What epidemiological term denotes the number of new cases of a disease that develop during a specific time period?
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Prevalence is the number of disease cases present in a particular population at a given time, whereas incidence is the number of new cases that develop during a specified time period. Prevalence is a snapshot of existing cases; incidence is a rate of new ones.