NBME CBSE study guide
NBME CBSE · Work through your exam, one topic at a time.
The NBME Comprehensive Basic Science Exam (CBSE) is a multiple-choice subject examination drawn from NBME's basic science item pool and administered through medical schools, most often to students in the preclinical years. It is an educational instrument rather than a licensing decision: it gives students and their schools a standardized, externally benchmarked picture of how well the foundational sciences - the organ systems plus the general principles that cut across them - have been consolidated before clinical training begins. The NBME CBSE study guide has 12 sections and about 3,846 words.
01Behavioral Health
Most missed behavioral-health items are time-based. Schizophrenia needs continuous signs for at least 6 months with at least 1 month of active symptoms; schizophreniform disorder is the same picture for 1–6 months; brief psychotic disorder lasts under 1 month.
290 words, about 1 min02Biostatistics, Epidemiology, and Population Health
Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); positive and negative predictive values depend on prevalence, while sensitivity and specificity do not (for a fixed cutoff). High sensitivity is good for ruling out (SnNout); high specificity is good for ruling in (SpPin).
381 words, about 2 min03Blood and Lymphoreticular System
Microcytic: iron deficiency (low ferritin, high TIBC, low saturation), thalassemia (normal or high ferritin, normal TIBC, target cells, elevated HbA2 in beta trait), anemia of chronic disease (low TIBC, normal or high ferritin, low saturation), lead poisoning (basophilic stippling), sideroblastic anemia (ring sideroblasts). Normocytic: acute blood loss, hemolysis, chronic kidney disease, aplastic anemia.
308 words, about 2 min04Cardiovascular System
Troponin rises at 3–6 hours and peaks near 24 hours; a single early normal value does not exclude myocardial infarction. ST elevation in contiguous leads localizes: II/III/aVF inferior (RCA), V1–V4 anterior (LAD), I/aVL/V5–V6 lateral (circumflex).
344 words, about 2 min05Endocrine System
Prolactinoma causes amenorrhea, galactorrhea, and bitemporal hemianopia. SIADH produces euvolemic hyponatremia with low serum osmolality, high urine osmolality, and urine sodium above 40; treat with fluid restriction.
291 words, about 1 min06Gastrointestinal System
Achalasia: progressive solid-then-liquid dysphagia with a bird's beak on barium swallow and loss of the myenteric plexus; raises squamous cell carcinoma risk. Esophageal cancer: progressive dysphagia and weight loss - squamous cell with smoking and alcohol, adenocarcinoma with Barrett esophagus.
293 words, about 1 min07General Principles of Foundational Science
Mitochondria perform oxidative phosphorylation and release cytochrome c during apoptosis; rough ER synthesizes protein; smooth ER handles detoxification and steroid synthesis; the Golgi modifies and sorts; lysosomes contain acid hydrolases; the proteasome degrades ubiquitin-tagged proteins. Apoptosis shows cell shrinkage, blebbing, and no inflammation and is caspase-dependent; necrosis shows swelling and inflammation.
319 words, about 2 min08Musculoskeletal, Skin, and Subcutaneous Tissue
Fractures are described by location, displacement, angulation, and open versus closed status; healing proceeds through hematoma, soft callus, hard callus, and remodeling. Compartment syndrome: pain out of proportion, pain with passive stretch, and paresthesias - pulselessness is a late finding; treatment is fasciotomy.
337 words, about 2 min09Nervous System and Special Senses
Upper motor neuron lesions cause spasticity, hyperreflexia, and an upgoing plantar response; lower motor neuron lesions cause flaccidity, atrophy, fasciculations, and areflexia. Broca aphasia is nonfluent with preserved comprehension; Wernicke aphasia is fluent with poor comprehension.
308 words, about 2 min10Renal and Urinary System
Glomerular filtration rate is best estimated by clearance; inulin is the gold standard and creatinine is the practical marker. Fractional excretion of sodium below 1% with oliguria suggests prerenal physiology; above 2% suggests acute tubular necrosis with muddy brown casts.
349 words, about 2 min11Reproductive System
Pulsatile GnRH drives FSH and LH; the LH surge triggers ovulation near day 14, and the corpus luteum produces progesterone for about 14 days. Estrogen produces midcycle ferning and proliferative endometrium; progesterone creates secretory endometrium and raises basal body temperature.
334 words, about 2 min12Respiratory System
Obstructive disease: reduced FEV1/FVC (below 0.70) with reduced FEV1 and increased residual volume and total lung capacity; asthma is reversible, COPD is not fully reversible. Restrictive disease: normal or high FEV1/FVC with reduced FVC and total lung capacity - interstitial lung disease, neuromuscular disease, obesity, and chest wall deformity.
292 words, about 1 min