Answers for the Bofs: Clinical sciences and statistics

1. A The absolute risk reduction is 5% and relative risk reduction is 20%B The number needed to treat = 1/absolute risk reduction 1/0.05 (i.e. 5%) = 20C D E Used for test values that are normally distributed

2. A The data are not normally distributed so a non-parametric test is indicated. Paired t-tests are not appropriate for unrelated samplesB Non-parametric test; Mann-Whitney U test can also be usedC Useful when observations are difficult to quantifyD Useful for analysing data grouped by category, e.g. eye colourE A 'correction' that is used when making multiple comparisons, to reduce the likelihood of false positive results.

3. A Used to compare data sets that have different variances or are non-normally distributedB C All reduce selection bias to reduce sampling errors, i.e. biases in the dataD E

4. A B The power of the study depends on the sample size, frequency of the main outcome measure, size of effect one wishes to detect, and the significance level desiredC D If patients drop out because of drug intolerance, this will reduce drug efficacy and reduce the power of

the study. An allowance for drop-outs is necessary in calculating the sample size requiredE By definition these are tests done in addition to the primary analysis and should not influence the sample size

calculation

5. A This is the modeB C D E

6. A Non-skewed or parametric dataB The mode is the value that occurs most frequently; the median is the middle valueC 95% is mean plus or minus two standard deviationsD Standard deviation of the mean divided by the square root of NE

7. A Pseudonym of the mathematician, William GossetB C D means not mediansE 95% confidence limits = (1.96 x standard error) < and > the mean

8. A The null hypothesis that there is no difference between groups is being testedB Often Yates correction required if numbers < 40 and this reduces value of chi-squareC D Any chance less than 1 in 20 (P < 0.05)E The test is designed to compare proportions rather than actual values, e.g. the number of patients losing

weight, not their mean weight loss

9. A This is the prevalence of a disease (includes all cases)B C Less than the prevalence; the incidence is the number of new cases arising each yearD E

10. A L-arginine is the substrate producing nitric oxide and L-citrullineB A vasodilator in systemic and pulmonary circulationsC Increases CGMPD Too highly reactive to be storedE Highly soluble due to its high affinity for haemoglobin

11. A It is synthesized and released by atrial myocytes in response to the stimulus of atrial stretchB It inhibits renin productionC Catalysed by guanylyl cyclaseD It is a vasodilator and lowers blood pressureE It inhibits vasopressin secretion

12. A Myelination increases the conduction velocityB Small fibres conduct more slowly than large onesC Due to inactivation of voltage-gated sodium channelsD Tetrodotoxin is produced by the puffer or blow fishE Repolarization results from the inhibition of sodium entry

13. A Normal blood glucose; peripheral perfusion is common in severe acidosis including diabetic ketoacidosisB Causes metabolic alkalosis with a normal anion gapC Unusual to get such severe lactic acidosisD May occur with aspirin (but respiratory alkalosis is more typical)E Alkalosis is characteristic

14. A It is synthesized in endothelial cells and acts on smooth muscle cellsB It is formed by the action of cyclo-oxygenase on arachidonic acidC Vasodilator lowering both systemic and pulmonary vascular resistanceD E PGE inhibits contractility of the non-pregnant uterus but stimulates the pregnant uterus

15. A Also glucose and fructoseB Glucose and galactoseC D Glucose dimerE Maltose polymer

16. A Error in converting phenylaianine to tyrosine (phenylalanine hydroxylase deficiency)B Error in tyrosinase pathway (tyrosinase deficiency)C Defective alpha-glucosidase affecting sphingolipid metabolismD Defective cystathione beta-synthaseE Defective branched chain keto-acid decarboxylase

17. A Each comprises four haem groupsB Each haem group binds one oxygen moleculeC The ferrous state (Fe²+); Fe³+, occurs in methaemoglobinaemiaD Contains four polypeptide chainsE HbA2 comprises two alpha and two delta chains

18. A Carboxyhaemoglobin shifts the curve to the leftB The effect of pH on the ODC is called the Bohr effectC 2,3 DPG lowers affinity of haemoglobin for O2D E

19. A Adrenaline (epinephrine) like glucagon promotes glycogenolysisB Increased muscle fatty acid utilizationC Increases fatty acid release from adipocytesD Increased hepatic ketone body productionE Unlike the beta receptors which activate adenyl cyclase

20. A And cracking of the skin around the mouth, ears and eyelidsB Peripheral neuropathyC Causes xerophthalmia, especially if complicated by measlesD Niacin deficiency causes pellagra (dermatitis, diarrhoea and dementia)E Causes both associated with megaloblastic anaemia

21. A Stimulated by nitrates, an effect mediated by nitric oxideB ANP and BNP both increase cyclic GMP levelsC D Phosphodiesterases mediate the degradation of CGMPE The NO-haem complex changes the molecule's shape resulting in a 200-fold increase in the catalytic effects of the

enzyme

22. A <5%B 15%C <5%D 75%E Negligible

23. A Cranial nerve XB Cranial nerve XIIC Cranial nerve V exits via the foramen rotundum and ovaleD E The foramen magnum contains the cranial nerve XI

24. A BronchodilatationB VasodilatationC Uterine relaxation in the pregnant stateD Increased sweat gland secretionE

25. A Supplied by the radial nerveB Supplied by the ulnar nerveC Also the opponens pollicisD Only the lateral two lumbricalsE Supplied by the radial nerve

26. A B 40 times greater in the intracellular compartmentC D E Similar concentrations in intra- and extracellular fluid

27. A Non-perfused lungB High V/Q ratioC No change overall in the V/Q ratioD High V/Q ratioE High V/Q ratio

28. A Reduces gastric emptyingB C Decreases motility due to labyrinthine stimulationD Decreases motilityE

29. A Co-localized with enteroglucagon - 'ileal + colonic brake'B Released from L cells in the distal ileum; reduces motilityC CGRP stimulates the release of VIP, decreasing motilityD Decreases motility and inhibits secretionE Released from N cells in the distal ileum

30. A B Autosomal recessiveC Autosomal recessiveD Autosomal recessiveE Autosomal recessive

31. A Autosomal dominant (Rendu-Osler-Weber syndrome)B Usually autosomal dominant affecting 1-2 per 10 000C Chromosome 13 defect causing hepato-lenticular degenerationD Autosomal dominantE X-linked dominant mode of inheritance predominates

32. A 50% of daughters are carriers. 50% of sons are affectedB All daughters of affected males are carriersC Because only the X chromosome is passed to daughtersD 1 in 4; 1 in 2 chance of being male; 1 in 2 chance of a male being affectedE Only usually affected in the homozygous state

33. A Acetyl CoA is the starting point of Kreb's energy-producing cycle with the production of oxaloacetateB Negative feedbackC Glucose-6-phosphate and fructose-6-phosphate are freely convertible but acetyl CoA promotes glucose-6-phosphate

and hence glycolysisD Unlike the Kreb's cycle which is energy-producingE Acetyl CoA is formed from the oxidative decarboxylation of pyruvate

34. A About 60% of VLDLB This is a constituent of HDLC About 5% of VLDLD About 14% of VLDLE About 7%

35. A lmmunofluorescence is a technique for assessingB cell and tissue structures to identify andC localize particulate proteins such asD immunoglobulinsE

36. A Secreted by transformed B lymphocytesB IgA; also produced in respiratory tractC IgG is the only immunoglobulin which crosses the placentaD E Involved in hypersensitivity reactions

37. A Both classical and alternative pathways produce C3 convertaseB Synthesized in liverC Alternative pathway; the classical pathway isD triggered when immune complex combines with ClqE Clq esterase deficiency produces congenital angio-oedema

38. A Bone mass declines (osteoporosis) but mineralization is normalB Reduced insulin sensitivity and glucose tolerance declinesC Limits ability to mount a tachycardiaD Decreased number of nephrons, GFR and medullary functionE Decreased function may contribute to increase in autoimmune disease

39. A Decreased below normal (normal value 4ºC)B Elderly can detect changes > 2ºC cf 1ºC change in younger peopleC Metabolic heat production is 50% < than younger peopleD Thyroid function is normalE Autonomic dysfunction impairs thermoregulation especially in the elderly

40. A Increased step length variabilityB Decreased step frequency and a slower gaitC A broader-based gaitD Shorter stepsE A-P sway is greater in females than men in all the adult age groups

41. A X-linked recessive; 50% daughters are carriers, 50% sons are affectedB C Remember only the X chromosome passes from father to daughtersD 1 in 4 chance of being affectedE Homozygosity in females

42. A 22 pairs plus two sex chromosomesB Gamete nuclei are haploidC The Y chromosome is the smallerD Fluorescent spots on interphase nuclei of male cellsE

43. A Direct copying of one strand of DNA occurs in all nucleiB C A cytoplasmic eventD Forms the processed MRNAE

44. A The eight essential amino acids areB methionine, lysine, tryptophan, phenylalanine,C leucine, isoleucine, threonine and valineD E

45. A Intrinsic protein tyrosine kinase activityB Inhibits adenylate cyclaseC Histamine 2 and prostacyclinD activate adenylate cyclaseE

46. A C-rasB C D E

47. A Rapidly as happens in fear or coldB Decreased rapidly as blood glucose risesC Increased slowly, in response to stressD Increased slowly, in response to hungerE Dependent on activated lipoprotein lipase

48. A GreaterB Subarachnoid spaceC D Total volume 120-150 mlE Produced by the choroid plexuses; arachnoid villi reabsorb CSF

49. A B Gram-positive coccusC Gram-positive aerobicD Gram-positive coccusE Flagellated spirochaete

50. A Vibration and proprioceptionB C Spinal cord ends at the first lumbar vertebraD Supplies principally the anterior (motor) componentsE