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Alle 15 spørgsmål i overblik

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1. 1. A newborn screening test flags high blood phenylalanine. Which enzyme is deficient in classic phenylketonuria?

   • A. Phenylalanine hydroxylase
   • B. Tyrosinase
   • C. Homogentisate oxidase
   • D. Branched chain alpha ketoacid dehydrogenase
   Vis svar og forklaring

   Svar: A. Phenylalanine hydroxylase

   Phenylalanine hydroxylase converts phenylalanine to tyrosine using tetrahydrobiopterin as a cofactor. When it is missing, phenylalanine builds up and tyrosine becomes an essential amino acid that has to come from the diet. The other enzymes map to different diseases: tyrosinase to albinism, homogentisate oxidase to alkaptonuria, and branched chain alpha ketoacid dehydrogenase to maple syrup urine disease.

2. 2. In a family pedigree, every child of an affected woman has the condition, while no child of an affected man has it. Which inheritance pattern does this fit?

   • A. Autosomal dominant
   • B. X linked recessive
   • C. Mitochondrial
   • D. Autosomal recessive
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   Svar: C. Mitochondrial

   Mitochondria are inherited from the egg, so a mother passes her mitochondrial DNA to all of her children and a father passes none of his. Severity often varies within the same family because of heteroplasmy, meaning the proportion of mutated mitochondria differs from cell to cell. Autosomal dominant transmission would come from either parent to about half the children, which is not what this pedigree shows.

3. 3. Complete the sentence.

   A test with high _____ is most useful for ruling a disease out when the result is negative, while a test with high _____ is most useful for ruling it in when the result is positive.

   Muligheder for felt 1: sensitivity, specificity, precision

   Muligheder for felt 2: reliability, specificity, precision, sensitivity

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   Svar: sensitivity, specificity

   Sensitivity is the fraction of people with the disease that the test calls positive, so a very sensitive test misses almost nobody and a negative result carries weight. Specificity is the fraction of healthy people the test calls negative, so a very specific test rarely cries wolf and a positive result carries weight. The usual shorthand is that a sensitive test rules out and a specific test rules in.

4. 4. The same diagnostic test is moved from a specialty clinic where the disease is common to a general screening population where it is rare. What happens?

   • A. Sensitivity falls and specificity rises
   • B. Positive predictive value falls while sensitivity and specificity stay the same
   • C. Positive predictive value stays the same because it is a fixed property of the test
   • D. Negative predictive value falls
   Vis svar og forklaring

   Svar: B. Positive predictive value falls while sensitivity and specificity stay the same

   Sensitivity and specificity are properties of the test itself and do not move with prevalence. Predictive values do. When prevalence drops, more of the positives are false positives, so positive predictive value falls while negative predictive value rises. This is why screening a low risk population with an imperfect test produces so many positives that turn out to be nothing.

5. 5. Which of the following statements describe a case control study?

   Vælg alle, der passer.

   • A. It starts with people who already have the outcome and looks backward at exposure
   • B. It measures the incidence of new disease directly
   • C. It reports an odds ratio rather than a relative risk
   • D. It is an efficient design for studying a rare disease
   • E. It follows disease free people forward in time until the outcome appears
   Vis svar og forklaring

   Svar: A. It starts with people who already have the outcome and looks backward at exposure, C. It reports an odds ratio rather than a relative risk, D. It is an efficient design for studying a rare disease

   A case control study picks cases and matched controls first, then asks about past exposure, which makes it fast and cheap for rare outcomes. Because the investigator chose how many cases to enroll, the design cannot measure incidence, so the effect measure is an odds ratio. Following disease free people forward and measuring incidence describes a cohort study, and recall bias is the classic threat to the case control design.

6. 6. Diphtheria toxin and Pseudomonas aeruginosa exotoxin A kill host cells by the same mechanism. Which one?

   • A. They cleave SNARE proteins and block neurotransmitter release
   • B. They bind MHC class II and the T cell receptor outside the antigen binding groove
   • C. They raise cyclic AMP by ADP ribosylating the Gs alpha subunit
   • D. They ADP ribosylate elongation factor 2 and shut down protein synthesis
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   Svar: D. They ADP ribosylate elongation factor 2 and shut down protein synthesis

   Both toxins transfer an ADP ribose group onto elongation factor 2, which halts translation and kills the cell. The other options are real mechanisms belonging to other toxins: SNARE cleavage is tetanus and botulinum toxin, superantigen binding is toxic shock syndrome toxin and streptococcal pyrogenic exotoxin A, and ADP ribosylation of Gs alpha is cholera toxin.

7. 7. A young boy has recurrent abscesses with catalase positive organisms, and a dihydrorhodamine flow cytometry test is abnormal. What is the underlying defect?

   • A. Defective NADPH oxidase in phagocytes
   • B. Failed B cell maturation from a BTK mutation
   • C. CD18 deficiency preventing leukocyte adhesion
   • D. Deficiency of the terminal complement components C5 through C9
   Vis svar og forklaring

   Svar: A. Defective NADPH oxidase in phagocytes

   Chronic granulomatous disease comes from a defective NADPH oxidase, so phagocytes cannot generate the respiratory burst that normally produces superoxide. Catalase positive organisms are the problem because they destroy their own hydrogen peroxide, leaving the phagocyte with nothing to borrow. The dihydrorhodamine test measures that burst directly, which is why it is abnormal here.

8. 8. Which mechanism defines a type II hypersensitivity reaction?

   • A. IgE bound to mast cells cross linked by antigen
   • B. IgG or IgM directed against an antigen on a cell surface or in the matrix
   • C. Antigen antibody complexes depositing in tissue and activating complement
   • D. Sensitized T cells releasing cytokines that recruit macrophages
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   Svar: B. IgG or IgM directed against an antigen on a cell surface or in the matrix

   Type II is antibody against a fixed target, so the damage is local to the cell or tissue carrying that antigen, through complement lysis, opsonization or interference with receptor function. Type I is the IgE and mast cell route, type III is circulating immune complexes that deposit wherever the blood takes them, and type IV is cell mediated and takes a day or more to appear.

9. 9. A drug binds the same site as an agonist but produces no response of its own. What does it do to the agonist dose response curve?

   • A. It lowers the maximal response and cannot be overcome by more agonist
   • B. It shifts the curve to the left and raises agonist potency
   • C. It binds a separate site and lowers the maximal response
   • D. It shifts the curve to the right with the maximal response unchanged
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   Svar: D. It shifts the curve to the right with the maximal response unchanged

   That description is a competitive antagonist. It competes for the same binding site, so enough agonist can outcompete it and still reach the full maximal effect, which shows up as a rightward shift with an unchanged plateau. A noncompetitive or irreversible antagonist behaves the way the other options describe, lowering the maximal response no matter how much agonist you add.

10. 10. Which drug and characteristic toxicity pairings are correct?

    Vælg alle, der passer.

    • A. Aminoglycosides and ototoxicity
    • B. Vincristine and hemorrhagic cystitis
    • C. Bleomycin and pulmonary fibrosis
    • D. Cisplatin and vitamin B12 deficiency
    • E. Doxorubicin and dilated cardiomyopathy
    Vis svar og forklaring

    Svar: A. Aminoglycosides and ototoxicity, C. Bleomycin and pulmonary fibrosis, E. Doxorubicin and dilated cardiomyopathy

    Aminoglycosides damage the hair cells of the inner ear and the kidney, bleomycin causes lung injury that can progress to fibrosis, and the anthracyclines cause a dose related dilated cardiomyopathy driven by free radical damage to myocardium. The two wrong pairs belong elsewhere: hemorrhagic cystitis is the classic cyclophosphamide toxicity from acrolein, and vincristine causes peripheral neuropathy. Cisplatin is nephrotoxic and ototoxic, not a cause of B12 deficiency.

11. 11. Complete the sentence.

    Nitric oxide relaxes vascular smooth muscle by activating guanylate cyclase, which raises intracellular _____.

    Muligheder for felt 1: cyclic AMP, cyclic GMP, inositol trisphosphate, calcium

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    Svar: cyclic GMP

    Nitric oxide diffuses from the endothelium into the smooth muscle cell and switches on soluble guanylate cyclase, so cyclic GMP rises and the cell relaxes. Phosphodiesterase type 5 breaks that cyclic GMP down, which is why inhibiting the enzyme amplifies the same pathway. Cyclic AMP and inositol trisphosphate are second messengers for different receptor families.

12. 12. A urinalysis shows red blood cell casts and dysmorphic red cells with mild proteinuria, and the blood pressure is high. Which process does this pattern point to?

    • A. Nephrotic syndrome from podocyte injury
    • B. A lower urinary tract infection
    • C. Glomerular inflammation, the nephritic pattern
    • D. Prerenal azotemia from volume loss
    Vis svar og forklaring

    Svar: C. Glomerular inflammation, the nephritic pattern

    Red cell casts form inside the tubule, so they prove the bleeding came from the glomerulus rather than lower down, and that inflammatory picture with hypertension is the nephritic pattern. The nephrotic pattern is the opposite balance, with heavy proteinuria above roughly 3.5 grams per day, low albumin, edema and fatty casts, and a bland sediment. Learning the two sediments as a pair is faster than memorizing each disease separately.

13. 13. Which findings fit an obstructive pattern on pulmonary function testing?

    Vælg alle, der passer.

    • A. A reduced FEV1 to FVC ratio
    • B. An increased total lung capacity from air trapping
    • C. An increased FEV1 to FVC ratio
    • D. A prolonged expiratory phase
    • E. A reduced total lung capacity with a normal FEV1 to FVC ratio
    Vis svar og forklaring

    Svar: A. A reduced FEV1 to FVC ratio, B. An increased total lung capacity from air trapping, D. A prolonged expiratory phase

    Obstruction means air leaves slowly, so FEV1 falls more than FVC, the ratio drops, expiration takes longer and air stays trapped, which raises residual volume and total lung capacity. Restriction is the mirror image: the lungs are small, so both FEV1 and FVC fall together and the ratio is normal or even high. Reading the ratio first and the volumes second sorts almost every pulmonary function question quickly.

14. 14. Which pathway carries pain and temperature sensation, and where does it cross the midline?

    • A. The dorsal column and medial lemniscus pathway, crossing in the medulla
    • B. The lateral corticospinal tract, crossing in the medulla
    • C. The spinothalamic tract, crossing in the spinal cord within a segment or two of where the fiber enters
    • D. The dorsal spinocerebellar tract, which does not cross at all
    Vis svar og forklaring

    Svar: C. The spinothalamic tract, crossing in the spinal cord within a segment or two of where the fiber enters

    Pain and temperature fibers synapse in the dorsal horn and then cross almost immediately in the anterior white commissure before ascending in the spinothalamic tract. Fine touch, vibration and proprioception travel up the same side in the dorsal columns and only cross in the medulla. That difference in crossing level is what produces the split findings of a spinal cord hemisection, with loss of pain and temperature on the opposite side and loss of vibration and position sense on the same side.

15. 15. Complete the sentence.

    Attributing your own unacceptable impulse or feeling to somebody else is the immature defense mechanism called _____.

    Muligheder for felt 1: displacement, sublimation, projection, reaction formation

    Vis svar og forklaring

    Svar: projection

    Projection puts the disowned feeling onto another person, as when someone who resents a colleague insists the colleague resents them. Displacement moves the feeling onto a safer target instead, reaction formation replaces it with the opposite behavior, and sublimation channels it into something socially useful, which makes sublimation the one mature mechanism in this list.

Hvad USMLE Step 1 faktisk tester

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Siden januar 2022 er Step 1 blevet rapporteret som bestået eller ikke bestået, uden en trecifret score. Den ændring gjorde ikke eksamen lettere, men den ændrede strategien omkring den. At jagte et højere tal giver ikke længere noget, så det fornuftige mål er solid, bred kunnen på tværs af hele indholdsoversigten i stedet for at presse de sidste par point ud af ét yndlingsfag.

Indholdet er organiseret langs to akser, systemer og processer, og det er bevidst integreret. Ét enkelt spørgsmål kan trække et genetikbegreb, en lægemiddelmekanisme og et fund fra et organsystem ind i én og samme sygehistorie. Den offentliggjorte indholdsoversigt på usmle.org lister fagene og deres omtrentlige vægtning.

Sådan bruger du smagsprøven, og sådan læser du de basale fag

De her 15 spørgsmål er kompakte frem for fuldlange sygehistorier, og de bliver med vilje på den basalfaglige side. De spørger, hvilket enzym der mangler, hvilken receptor et lægemiddel virker på, hvad et mønster i prøvesvarene peger på, og hvad der sker med den prædiktive værdi, når prævalensen falder. Klinisk viden og ræsonnement om behandling hører til Step 2, og søskendequizzen herunder dækker det område. Denne side er eksamenstræning skrevet af StudyPDF-teamet. Det er ikke medicinsk vejledning, det er ikke en kilde til beslutninger om patientbehandling, og ingen af spørgsmålene er rigtige eksamensspørgsmål.

Tag smagsprøven i ét stræk uden noter, og læs så hver eneste forklaring, også dem du svarede rigtigt på. Et forkert svar er et emne, ikke et faktum. Taber du spørgsmålet om sensitivitet og spørgsmålet om prædiktiv værdi, er løsningen en eftermiddag med testegenskaber, ikke to flashcards.

Til selve eksamen er det studiemønster, der virker, en lang periode med blandede øvespørgsmål og gentagelse over tid, ikke ét gennemløb af en repetitionsbog. Lav spørgsmål i tilfældig rækkefølge på tværs af fag, så du er nødt til at gennemskue, hvad spørgsmålet i virkeligheden tester, og før en løbende liste over de begreber, du rammer forkert.

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StudyPDF arbejder ud fra dit materiale i stedet. Du uploader dine forelæsningsslides, dine handouts fra patologi, et kursuskompendium eller den repetitionsbog, du allerede ejer, og Bo, studieagenten, skriver øvespørgsmål ud fra præcis de sider. Hvert spørgsmål bygger på det, du har uploadet, og hver forklaring peger tilbage på, hvor svaret kom fra, så du kan gå direkte til kilden, når noget ser forkert ud. Du kan lave nye sæt så tit du vil, holde et sæt på ét system som nyrer eller hormoner, og følge med i hvilke begreber der bliver ved med at drille.

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