Arab Board Community Medicine Final Written cheat sheet

Incidence counts new cases arising in a population at risk over a defined period; cumulative incidence = new cases ÷ population at risk at the start, while incidence rate = new cases ÷ person-time of observation.

In a steady state, prevalence ≈ incidence × mean duration of disease; prevalence rises when incidence increases or when survival with the disease lengthens.

Relative risk = incidence in exposed ÷ incidence in unexposed. The odds ratio approximates relative risk only when the outcome is rare, roughly under 10%.

Attributable risk (risk difference) = Ie − Iu. Population attributable fraction = Pe(RR − 1) ÷ [1 + Pe(RR − 1)], where Pe is the prevalence of exposure in the population.

Sensitivity = TP ÷ (TP + FN); specificity = TN ÷ (TN + FP); PPV = TP ÷ (TP + FP); NPV = TN ÷ (TN + FN). Sensitivity and specificity are properties of the test, whereas PPV and NPV shift with prevalence.

Herd immunity threshold = 1 − 1/R0. Measles with R0 of 12–18 requires about 92–95% population immunity, whereas influenza with R0 near 2 requires about 50%.

Bradford Hill viewpoints include temporality, strength, consistency, biological gradient, plausibility, coherence and experiment; temporality is the only indispensable criterion.

Screening biases: lead-time bias lengthens measured survival without postponing death; length bias over-selects slowly progressive disease; overdiagnosis detects lesions that would never cause harm; selection bias affects who is screened.

Standard error of the mean = SD ÷ √n; the 95% confidence interval for a mean is mean ± 1.96 SE, or mean ± t(SE) when the sample is small.

In a normal distribution about 68% of observations lie within 1 SD of the mean, 95% within 1.96 SD, and 99.7% within 3 SD.

Type I error (alpha) is a false-positive conclusion, conventionally 0.05; type II error (beta) is a false negative; power = 1 − beta and is conventionally at least 80%.

Sample size for a proportion: n = Z²p(1 − p) ÷ d²; for a mean: n = (Zσ ÷ d)². Required size rises with variance and confidence level and falls as the acceptable error d increases.

Test selection: chi-square for two categorical variables, McNemar for paired binary data, independent t-test for two means, paired t-test for repeated means, ANOVA for three or more means; use Mann–Whitney or Kruskal–Wallis when normality fails.

Pearson correlation is used for two continuous normally distributed variables and Spearman for ordinal or non-normal data; a strong correlation does not by itself establish causation.

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

Regression choice: linear regression for a continuous outcome, logistic regression for a binary outcome (reports odds ratios), Cox proportional hazards for time-to-event data (reports hazard ratios).

Intention-to-treat analysis keeps every randomised participant in the group to which they were allocated, preserving randomisation and protecting against attrition bias.

Management functions follow POSDCORB: planning, organising, staffing, directing, coordinating, reporting and budgeting; control closes the cycle by comparing actual performance with agreed standards.

Unity of command means each employee reports to one supervisor; span of control is the number of direct reports, with narrow spans giving closer supervision and wide spans producing flatter structures.

Maslow's hierarchy runs physiological → safety → social belonging → esteem → self-actualisation; lower-order needs generally require attention before higher-order ones motivate behaviour.

Herzberg's two-factor theory: hygiene factors such as pay, policy and working conditions prevent dissatisfaction but do not motivate; motivators such as achievement, recognition, responsibility and growth produce satisfaction.

McGregor's Theory X assumes workers avoid responsibility and need close control, while Theory Y assumes self-direction and supports participative management.

SWOT analysis maps internal strengths and weaknesses against external opportunities and threats; the TOWS variant converts these into SO, ST, WO and WT strategies.

Donabedian's quality framework runs structure → process → outcome; clinical audit compares observed practice with explicit standards and closes the loop with re-audit after implementing change.

Budget formats: line-item budgets control inputs, programme budgets follow objectives, performance budgets link spending to measurable outputs, and zero-based budgets require every activity to be justified from zero each cycle.

Conflict-handling modes are avoiding, accommodating, competing, compromising and collaborating; collaborating pursues a win–win outcome and suits important issues where time allows.

The planning cycle runs: situation analysis → priority setting → SMART objectives → strategies and activities → implementation → monitoring and evaluation → replanning.

Priority-setting criteria include disease burden, severity, cost-effectiveness, equity, feasibility, community demand and political support.

Types of economic evaluation: cost-minimisation analysis when outcomes are equivalent, cost-effectiveness analysis with natural health units, cost-utility analysis using QALYs or DALYs, and cost-benefit analysis with all outcomes monetised.

Incremental cost-effectiveness ratio = (Cost of A − Cost of B) ÷ (Effect of A − Effect of B); an intervention is judged worthwhile when its ICER falls below the local willingness-to-pay threshold.

QALY = years of life × utility weight, where 0 represents death and 1 perfect health; DALY = years of life lost from premature death + years lived with disability.

Health financing functions are revenue collection, pooling and purchasing; universal health coverage is summarised by the cube of population covered, services covered and proportion of costs covered.

Out-of-pocket payment is the least protective financing mechanism; prepayment with risk pooling spreads the cost of illness across healthy and sick and across time.

Policy analysis triangle: context, content, and actors/process; evaluation types are formative, process, impact and outcome evaluation, each answering a different question.

Costs in economic evaluation are classified as direct (medical and non-medical) versus indirect (productivity loss), and fixed versus variable; the perspective chosen (provider or societal) determines which costs are counted.

Hierarchy of controls, most to least effective: elimination, substitution, engineering controls, administrative controls, then personal protective equipment.

Occupational exposure limits: TLV-TWA applies to a conventional 8-hour shift, TLV-STEL to a 15-minute peak (maximum four per day with rests between), and ceiling limits must never be exceeded.

Noise-induced hearing loss risk rises with intensity, duration and impulsiveness; hearing conservation programmes are triggered at 85 dBA averaged over 8 hours.

Pneumoconioses are irreversible, so prevention is primary: silicosis from crystalline silica, asbestosis with excess mesothelioma and lung cancer, and coal workers' pneumoconiosis.

Lead exposure causes anaemia, peripheral neuropathy, hypertension and nephrotoxicity; blood lead concentration is the standard biomarker of recent exposure.

Drinking-water safety relies on source protection, adequate treatment, free chlorine residual of at least 0.2 mg/L at the point of delivery, and turbidity below 5 NTU so that disinfection remains effective.

The sanitation ladder runs from open defecation to unimproved, shared, basic and safely managed services; safely managed adds treatment and safe disposal off-site.

Fine particulate matter (PM2.5) shows the most consistent association with mortality; indoor biomass smoke, second-hand tobacco smoke and radon are major indoor air risks.

Integrated vector management combines source reduction, biological control, larviciding, adulticiding and personal protection, selected according to local vector ecology and insecticide resistance data.

The Ottawa Charter (1986) sets five action areas: build healthy public policy, create supportive environments, strengthen community action, develop personal skills, and reorient health services.

Levels of prevention: primordial (avoiding risk-factor formation), primary (before disease onset), secondary (early detection and prompt treatment) and tertiary (limiting disability and rehabilitating).

Health Belief Model constructs are perceived susceptibility, perceived severity, perceived benefits, perceived barriers, cues to action and self-efficacy.

Stages of change: precontemplation, contemplation, preparation, action, maintenance and possible relapse; interventions are matched to the person's current stage rather than delivered uniformly.

PRECEDE-PROCEED diagnoses predisposing, enabling and reinforcing factors before programme design, then evaluates process, impact and outcome in the PROCEED phase.

Social Cognitive Theory holds that person, behaviour and environment interact reciprocally; self-efficacy and observational learning are its central determinants of behaviour.

Diffusion of innovations adopter categories are innovators, early adopters, early majority, late majority and laggards; adoption of the early majority marks the tipping point for spread.

Health education targets individual knowledge, attitudes and skills, whereas health promotion additionally uses policy, environmental change and community mobilisation.

Health literacy is the capacity to obtain, process and understand health information to make appropriate decisions; low health literacy is associated with poorer adherence and worse outcomes.

Chain of infection: infectious agent → reservoir → portal of exit → mode of transmission → portal of entry → susceptible host. Control measures can interrupt any one of these links.

Droplets exceed 5 micrometres, travel under about 1 metre and require droplet precautions; airborne particles below 5 micrometres remain suspended and require airborne precautions, as for tuberculosis, measles and varicella.

Herd immunity threshold = 1 − 1/R0; approximate values are 92–95% for measles, 80–85% for poliomyelitis and about 85% for diphtheria.

The incubation period runs from exposure to onset of symptoms, the latent period from exposure to becoming infectious, and the infectious period determines how long isolation or exclusion is required.

Outbreak investigation: confirm the diagnosis, define a case, search for cases, describe by time, place and person, generate hypotheses, test them with an analytic study, institute control measures, and write the report.

Surveillance types: passive (routine reporting by facilities), active (health workers actively seek cases), sentinel (selected reporting sites) and syndromic (monitoring symptom clusters before diagnosis).

Tuberculosis treatment is 2 months of isoniazid, rifampicin, pyrazinamide and ethambutol followed by 4 months of isoniazid and rifampicin, supervised as DOTS with contact tracing; latent infection uses shorter regimens.

Cold chain: most vaccines are held at +2 to +8 degrees Celsius, oral polio vaccine is stored frozen, and adsorbed vaccines such as DTP, hepatitis B and tetanus toxoid must never be frozen.

Vaccine types: live attenuated vaccines (BCG, MMR, oral polio, yellow fever) replicate in the host and are contraindicated in severe immunosuppression; inactivated, toxoid, subunit and mRNA vaccines do not replicate.

The four main NCDs are cardiovascular disease, cancer, diabetes and chronic respiratory disease; they share four modifiable risk factors: tobacco use, unhealthy diet, physical inactivity and harmful use of alcohol.

Hypertension is defined as systolic pressure at least 140 mmHg or diastolic pressure at least 90 mmHg on repeated measurement; lifestyle change plus pharmacotherapy reduces stroke and coronary events.

Diabetes diagnosis uses fasting plasma glucose of 7.0 mmol/L (126 mg/dL) or more, 2-hour OGTT of 11.1 mmol/L (200 mg/dL) or more, or HbA1c of 6.5% or more.

Body mass index = weight in kilograms ÷ height in metres squared; underweight is below 18.5, normal 18.5–24.9, overweight 25–29.9 and obesity 30 or above.

Tobacco control uses MPOWER: Monitor use, Protect people from smoke, Offer help to quit, Warn about harms, Enforce advertising bans and Raise taxes.

Cancer screening examples: cervical HPV testing starting around age 30, mammography for breast cancer in women aged 50–69, and faecal immunochemical testing or colonoscopy for colorectal cancer.

DALY = years of life lost from premature death + years lived with disability, combining mortality and morbidity into one burden metric for priority setting.

Secondary prevention after myocardial infarction comprises aspirin, a statin, a beta-blocker and an ACE inhibitor, together with blood pressure, glycaemic and smoking control.

WHO/ISH or locally validated risk charts estimate 10-year cardiovascular risk and determine whether antihypertensive and lipid-lowering treatment should be started.

SDG 3 targets for 2030: maternal mortality ratio below 70 per 100,000 live births, neonatal mortality at most 12 and under-5 mortality at most 25 per 1,000 live births.

WHO's 2016 antenatal model recommends at least eight contacts, with the first before 12 weeks of gestation, replacing the earlier four-visit focused antenatal care package.

Obstetric danger signs include vaginal bleeding, severe headache or blurred vision, convulsions, fever, difficulty breathing, reduced fetal movements and prolonged or obstructed labour.

Postnatal contacts are scheduled within 24 hours, on day 3, between days 7 and 14, and at 6 weeks, covering breastfeeding, danger signs, immunisation and family planning.

Infant feeding: exclusive breastfeeding for the first 6 months, complementary foods from 6 months, and continued breastfeeding up to 2 years or beyond.

Growth assessment distinguishes stunting (low height-for-age), wasting (low weight-for-height) and underweight (low weight-for-age); each reflects a different underlying process.

IMCI assesses and classifies sick children by danger signs into urgent referral, specific treatment or home care, integrating nutrition, immunisation and counselling of the caregiver.

Kangaroo mother care for low birth weight infants combines skin-to-skin contact, exclusive breastfeeding and close follow-up, reducing mortality, hypothermia and infection.

Adolescent health priorities include HPV vaccination, mental health, substance use, nutrition and anaemia, sexual and reproductive health, and injury prevention.

The Alma-Ata Declaration (1978) made primary health care the key to Health for All; the Astana Declaration (2018) reaffirmed primary health care as the foundation of universal health coverage.

Starfield's attributes of primary care are first contact, continuity, comprehensiveness and coordination; accessibility and community orientation are commonly added.

Family medicine principles: patient-centred, family-oriented, community-based, continuous, comprehensive and coordinated care delivered through the biopsychosocial model.

SOAP documentation comprises Subjective, Objective, Assessment and Plan; the problem-oriented record links every identified problem to its own assessment and plan.

The Calgary–Cambridge consultation framework covers initiating the session, gathering information, physical examination, explanation and planning, closing the session, and building rapport throughout.

Gatekeeping means the primary care physician coordinates access to specialist care using explicit referral criteria, with safety-netting advice so that serious illness is not missed.

Wagner's chronic care model combines community resources and policies, health system organisation, self-management support, delivery system design, decision support and clinical information systems.

Community diagnosis uses quantitative and qualitative methods to describe the population's health status, resources and priorities, and it feeds directly into the local health plan.

The clinical audit cycle: define standards, collect data, compare practice with the standards, implement change, then re-audit to confirm improvement.