Arab Board Community Medicine Part 1 cheat sheet

Incidence rate = new cases in a period / population at risk during that period; it measures risk and has units of per person-time.

Prevalence = incidence × average duration of disease (when disease is in steady state); prevalence rises when incidence or survival increases.

Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); both are properties of the test, unaffected by prevalence.

Positive predictive value = TP/(TP+FP); PPV rises with higher prevalence, so a test's predictive value differs between settings.

Odds ratio approximates relative risk only when the outcome is rare (roughly under 10%).

Attributable risk (risk difference) = incidence in exposed minus incidence in unexposed; population attributable fraction = Pe(RR−1)/(1+Pe(RR−1)).

Crude rates are confounded by age structure; direct standardisation applies study age-specific rates to a reference population, indirect standardisation yields an SMR.

95% confidence interval for a mean = mean ± 1.96 × standard error, where standard error = SD/√n.

A p-value is the probability of data at least as extreme as observed if the null hypothesis is true; it is not the probability the null is true.

Levels of prevention: primordial (risk-factor avoidance in society), primary (pre-disease), secondary (early detection), tertiary (disability limitation), quaternary (avoiding overmedicalisation).

Screening is justified when the condition is important, has a detectable latent stage, an acceptable test, and effective early treatment; Wilson–Jungner criteria.

Lead-time bias makes screening appear to prolong survival without changing the time of death; length bias over-selects slowly progressive cases.

Herd immunity threshold = 1 − 1/R0; measles R0 of 12–18 requires roughly 92–95% coverage.

Notifiable disease surveillance is passive; sentinel and active surveillance are more sensitive but costlier.

Years of life lost (YLL) plus years lived with disability (YLD) sum to disability-adjusted life years (DALY).

Sensitivity of a screening programme depends on test sensitivity, coverage, and repeat screening frequency, not test sensitivity alone.

Donabedian's triad: structure (inputs), process (activities), outcome (results) - quality is assessed across all three.

Leadership styles: autocratic (fast, low morale), democratic (participative, slower), laissez-faire (delegative, low control).

Management cycle: planning, organising, staffing, directing, coordinating, reporting, budgeting (POSDCORB).

SWOT analysis maps internal strengths and weaknesses against external opportunities and threats.

Health system building blocks (WHO): service delivery, workforce, information, medical products, financing, leadership/governance.

Cost-effectiveness analysis compares cost per unit of health outcome; cost-benefit expresses both costs and outcomes in monetary terms.

Universal health coverage has three dimensions: population covered, services covered, and proportion of costs covered.

Hierarchy of occupational hazard control: elimination, substitution, engineering controls, administrative controls, personal protective equipment (least effective).

PM2.5 penetrates alveoli and is the air pollutant most consistently linked to cardiopulmonary mortality; WHO guideline is 5 µg/m³ annual mean.

Water chlorination prevents cholera and typhoid; residual free chlorine of about 0.2–0.5 mg/L is maintained in distribution.

Threshold limit values (TLVs) are time-weighted averages for an 8-hour workday, 40-hour week; short-term exposure limits cover 15 minutes.

Biological monitoring measures internal dose (e.g., blood lead, urinary metabolites) and reflects total exposure from all routes.

Noise-induced hearing loss begins at 4 kHz; risk rises above 85 dBA over an 8-hour exposure.

Carbon monoxide binds haemoglobin with about 200–250 times the affinity of oxygen, causing tissue hypoxia.

Maternal mortality ratio = maternal deaths per 100,000 live births; the denominator is live births, not women.

Antenatal care: WHO recommends at least 8 contacts; the first contact should occur before 12 weeks.

Exclusive breastfeeding is recommended for the first 6 months, with complementary feeding from 6 months and continued breastfeeding to 2 years.

Neonatal mortality = deaths in the first 28 days per 1,000 live births; it is the largest component of under-5 mortality in many settings.

WHO partograph is used to monitor labour progress and detect prolonged or obstructed labour early.

Magnesium sulfate is the drug of choice for prevention and treatment of eclampsia and severe pre-eclampsia.

Growth monitoring uses weight-for-age, height-for-age, and weight-for-height; weight-for-height detects acute malnutrition.

Attack rate = cases among exposed / total exposed; useful in food-borne and point-source outbreaks.

R0 is the basic reproduction number in a fully susceptible population; Reff = R0 × proportion susceptible.

Case fatality rate = deaths among diagnosed cases / diagnosed cases; it differs from infection fatality rate, which includes undiagnosed infections.

Incubation period determines quarantine duration and the window for post-exposure prophylaxis.

Contact tracing aims to identify and isolate exposed contacts before they become infectious (ring containment).

Vector control for malaria relies on indoor residual spraying and insecticide-treated nets; larviciding targets breeding sites.

Tuberculosis treatment uses a 6-month regimen with rifampicin; adherence and drug susceptibility testing prevent resistance.

NCDs account for roughly 70% of global deaths; cardiovascular disease, cancer, diabetes, and chronic respiratory disease are the four main groups.

Modifiable risk factors include tobacco, harmful alcohol use, unhealthy diet, physical inactivity, and air pollution.

The Ottawa Charter (1986) identified five action areas: healthy public policy, supportive environments, community action, personal skills, and reorientation of health services.

The health belief model explains behaviour via perceived susceptibility, severity, benefits, barriers, and cues to action.

Transtheoretical model stages: precontemplation, contemplation, preparation, action, maintenance, and relapse.

BMI = weight (kg) / height (m)²; obesity is BMI ≥ 30, overweight BMI 25–29.9.

Screening for hypertension and diabetes in adults is a core secondary-prevention strategy in primary care.

Protein-energy malnutrition: marasmus is severe wasting without oedema; kwashiorkor is oedema with low serum albumin.

Exclusive breastfeeding provides about 0.67 kcal/mL and enough water for the first 6 months in a healthy infant.

Iodine deficiency causes goitre and cretinism; universal salt iodisation is the main control measure.

Vitamin A deficiency causes night blindness and xerophthalmia; supplementation is given to children 6–59 months.

Iron deficiency is the most common micronutrient deficiency; iron absorption is enhanced by vitamin C and inhibited by phytates and tannins.

HACCP is a seven-principle food safety system: hazard analysis, CCPs, limits, monitoring, corrective actions, verification, and records.

Food-borne outbreak investigation: form a case definition, generate hypotheses, conduct a case-control or cohort study, then implement control.

Study designs: randomised controlled trial (strongest for causation), cohort (incidence, relative risk), case-control (rare outcomes, odds ratio), cross-sectional (prevalence).

Randomisation balances known and unknown confounders; blinding reduces measurement and observer bias.

Sampling: simple random, systematic, stratified, cluster, and multistage; probability sampling supports generalisation.

Sample size for a proportion: n = Z² P(1−P)/d²; multiply by a design effect for cluster sampling.

Electronic health records support clinical care and secondary use; data governance covers consent, privacy, and access control.

Data quality dimensions include completeness, accuracy, timeliness, consistency, and validity.

Confounding is a third variable associated with both exposure and outcome; it is addressed by design (randomisation) or analysis (stratification, regression).