ABPM Occupational Medicine cheat sheet

Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); a highly sensitive test is best for ruling out disease when negative (SnNout).

Positive predictive value = TP/(TP+FP) and depends on prevalence; PPV falls as prevalence falls even with unchanged sensitivity and specificity.

Number needed to treat = 1/absolute risk reduction; NNT = 1/(control event rate − treatment event rate).

Relative risk = incidence in exposed / incidence in unexposed; attributable risk = incidence in exposed − incidence in unexposed.

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

Screening test criteria: important disease, acceptable treatment, detectable preclinical phase, suitable test with adequate sensitivity/specificity, and evidence that early detection improves outcomes.

Lead-time bias makes survival appear longer after screening without changing the time of death; length bias overrepresents slowly progressive cases.

Herd immunity threshold ≈ 1 − 1/R0; measles R0 of roughly 12–18 requires about 92–95% population immunity.

Levels of prevention: primary (pre-exposure), secondary (early detection/screening), tertiary (limiting disability from established disease).

OSHA permissible exposure limits are 8-hour time-weighted averages; the action level is typically one-half the PEL and triggers exposure monitoring and medical surveillance.

Noise: 85 dBA 8-hour TWA is the OSHA action level; hearing conservation program required at 85 dBA, and a standard threshold shift is a 10 dB average shift at 2000, 3000, and 4000 Hz.

Asbestos exposure causes asbestosis, lung cancer, mesothelioma, and pleural plaques; latency for malignancy is typically 20–40 years, and smoking multiplies lung cancer risk synergistically.

Silicosis is caused by respirable crystalline silica; acute silicosis follows intense exposure within weeks to years, and silicosis increases risk of tuberculosis.

Lead exposure causes anemia (basophilic stippling), peripheral neuropathy, hypertension, and nephropathy; elevated blood lead triggers removal from exposure under OSHA medical removal provisions.

Benzene is a recognized leukemogen (acute myeloid leukemia); chronic exposure also causes bone marrow suppression and aplastic anemia.

Carbon monoxide binds hemoglobin with roughly 200–250 times the affinity of oxygen; treatment is removal from source and high-flow oxygen, with hyperbaric oxygen for severe cases.

Occupational asthma is suggested by symptoms improving away from work; serial peak flow measurements at and away from work support the diagnosis.

PELs are enforceable legal limits, whereas ACGIH TLVs and NIOSH RELs are recommended, non-regulatory values.