clinical sci Flashcards
what is the equation for systemic vascular resistance?
Systemic vascular resistance = mean arterial pressure / cardiac output
what is meant by numbers needed to treat (NNT)?
a measure that indicates how many patients would require an intervention to reduce the expected number of outcomes by one
calculated by 1/(Absolute risk reduction)
e.g. control group 4%, test group 2% risk
0.04-0.02 = absolute risk reduction
1/0.02 = 50 = NNT
what is the EER and CER in a study?
Experimental event rate (EER) = (Number who had particular outcome with the intervention) / (Total number who had the intervention)
Control event rate (CER) = (Number who had particular outcome with the control/ (Total number who had the control)
how is relative risk calculated?
relative risk = ratio of contol to test group
e.g 100 patient take control and test drug. of control 50 develop disease, of tes 30 develop disease
relative risk = 03/0.5 = 0.6
if <1 then test drug works
what is relative risk reduction/ increase?
divide difference in risk by control rate
e.g
e.g 100 patient take control and test drug. of control 50 develop disease, of tes 30 develop disease
relative risk = 0.5-0.3 = 0.2
relative risk reduction = 0.2/0.5 = 40%
what is the Fab and Fc region of Antibodies?
Fab - antigen binding fragment
Fc - constant region
what is the most common type of antibody found in the body?
IgG
which is the predominant Ab in breast milk?
IgA
which is the first Ab to be secreted in infection?
IgM
which Ab mediated type 1 hydpersensitivity?
IgE
which Ab is least abudant in serum?
IgE
which Ab protects against worms/ helminths?
IgE
where is ADH produced?
supraoptic nucleus of hypothalamus
what is the function of Anakinra
IL1 receptor antagonist
used in rheumatoid arthritis
which cells produce the following cytokines... IL1 IL2 IL3 IL4 IL5 IL6 IL8 IL10
IL1 - macrophages (fever, inflammation) IL2 - Th1 cells IL3, IL4, IL5 - Th2 cells IL6 - macrophages and TH2 IL8 - macrophages (neutrophil chemotaxis) IL10 - Th2
which cells produce the following cytokines…
TNFa
IFNg
TNFa - macrophages (induces fever, neutrophil chemotaxis)
IFNg - TH1 (activates macrophages)
which type of cancer should the following suggest…
Persistent unexplained hoarseness or pain in the throat, particularly in smokers with significant unexplained weight loss
oropharyngeal
risk factors - HPV
which cancers is EBV linked to?
Burkitt’s lymphoma
Hodgkin’s lymphoma
Post transplant lymphoma
Nasopharyngeal carcinoma
which cancers is HPV 16/18 linked to?
Cervical cancer Anal cancer Penile cancer Vulval cancer Oropharyngeal cancer
which cancer is the following linked to
Herpes virus 8
HTLV1
Herpes - Kaposi sarcoma
HTLV1 - adult T cell lymphoma
what type of disease is Leber’s optic atrophy
mitochondrial - maternal inheritance
what type of inheritance is seen with mitochondrial diseases?
affected man - none of children inherit
affected woman - all of children inherit.
in mitochondrial disease, what does muscle biopsy often show?
muscle biopsy classically shows ‘red, ragged fibres’ due to increased number of mitochondria
Giv examples of mitochondrial diseases…
Leber’s optic atrophy
MELAS syndrome: mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes
MERRF syndrome: myoclonus epilepsy with ragged-red fibres
Kearns-Sayre syndrome: onset in patients < 20 years old, external ophthalmoplegia, retinitis pigmentosa.
sensorineural hearing loss
describe steps of cardiac action potential…
Na in - depolatisation
K out - a little repolarisation
K out and Ca in - levels out the repolarisatin
K out only - repolarises
what is meant by parametric and non-parametric tests?
parametric - something that fits a normal distributed.
non-parametric - not normally distributed.
give examples of a parametric test
Student’s t-test - paired or unpaired*
Pearson’s product-moment coefficient - correlation
give examples of a non-parametric test and give a breif description.
Mann-Whitney U test
compares ordinal, interval, or ratio scales of unpaired data
Wilcoxon signed-rank test
compares two sets of observations on a single sample, e.g. a ‘before’ and ‘after’ test on the same population following an intervention
chi-squared test
used to compare proportions or percentages e.g. compares the percentage of patients who improved following two different interventions
Spearman, Kendall rank - correlation
what are the characteristics of congnital CMV infection?
growth retardation purpuric skin lesions - blueberry muffin skin Sensorineural deafness Encephalitis/seizures Pneumonitis Hepatosplenomegaly Anaemia Jaundice Cerebral palsy
what are the characteristics of congnital toxoplasmosis infection?
Cerebral calcification Chorioretinitis Hydrocephalus Hepatosplenomegaly Cerebral palsy anaemia
Congenital toxoplasmosis is the classic triad of cerebral calcification, chorioretinitis and hydrocephalus.
Can present later in childhood.
what are the characteristics of coggenital rubella infection?
Sensorineural deafness, cerebral palsy
Congenital cataracts, Glaucoma, ‘Salt and pepper’ chorioretinitis, Microphthalmia
Congenital heart disease (e.g. patent ductus arteriosus)
Growth retardation
Hepatosplenomegaly
Purpuric skin lesions - blueberry muffin rash
typically presents at birth
what is the function of the following cranial nerves…
a) I
b) II
c) III
d) IV
a) olfactory
b) optic
c) occulomotor - eye movement, pupil contriction, accomodation, eyelid opening
d) trochlea - eye movement
what is the function of the following cranial nerves…
a) V
b) VI
c) VII
d) VIII
a) trigeminal - facial sensation, mastication
b) abducens - eye movement
c) facial - face movements, tasteant 2/3, lacrimation, salivation
d) vesticulocochlea- hearing and balance
what is the function of the following cranial nerves…
a) IX
b) X
c) XI
d) XII
a) glossopharyngeal - swallow, post 1/3 taste, carotid sinus input
b) vagus - phonation, swallow
c) accessory - head and shoulder movement
d) hypoglosal - tongue movement
describe cranial nerve palsies III, IV and VI
III - Palsy results in ptosis, ‘down and out’ eye, dilated, fixed pupil
IV - Palsy results in defective downward gaze → vertical diplopia
VI- Palsy results in defective abduction → horizontal diplopia
describe cranial nerve palsy X and XII
X - uvula deviates away from site of lesion
XII - tongue deviates towards site of lesion.
which nerves are involved in the following reflexes.... corneal jaw jerk gag pupilary light lacrimation
corneal - opthalmic and facial jaw jerk - trigeminal gag - glossopharyngeal, vagus pupillary light - optic, occulomotor lacrimation - opthalmic, facial.
first = sensory, second = motor
what is sensitivity?
Proportion of patients with the condition who have a positive test result
what is specificity?
Proportion of patients without the condition who have a negative test result
what is positive predictive value?
The chance that the patient has the condition if the diagnostic test is positive
what is the negative predictive value?
The chance that the patient does not have the condition if the diagnostic test is negative
which cells produce the different interferons?
IFNa - leukocytes - antiviral actions
IFNb - fibroblasts - antiviral action.
IFNg - NK and T helper cells.- granulomatous disease
what is the chloride shift in RBC?
Chloride shift
CO2 diffuses into RBCs
CO2 + H20 —- carbonic anhydrase -→ HCO3- + H+
H+ combines with Hb
HCO3- diffuses out of cell,- Cl- replaces it
what is haldane effect?
increase pO2 means CO2 binds less well to Hb
when are levels of endothelin raised?
MI heart failure ARF asthma primary pulmonary hypertension
what inhibits the release of endothelin?
NO
prostacyclin
what promotes the release of endothelin?
ADH
angiotensin,
sheer stress
hypoxia
what immunological changes are seen in progressive HIV?
reduction in CD4 count increase B2-microglobulin decreased IL-2 production polyclonal B-cell activation decrease NK cell function reduced delayed hypersensitivity responses
what are the roots of the radial nerve?
C5 to T1
what is the function of the radial nerve?
motor:
Triceps, Anconeus, Brachioradialis, Extensor carpi radialis, Supinator, Abductor pollicis longus and all other extensor muscles
sensory: dorsal aspect of hand except little and rign finger.
what happens if radial nerve is damaged?
at axila…
wrist drop
sensory loss to small area between the dorsal aspect of the 1st and 2nd metacarpals
and paralysis of triceps
how is standard error of mean calculateD?
SD / square root (n)
standard deviation / square root of number of people
how are 95% confidence intervals calculated?
A 95% confidence interval:
lower limit = mean - (1.96 * SEM)
upper limit = mean + (1.96 * SEM)
how is the power of a study calculated?
Power = 1 - the probability of a type II error
Power means correctly identifying the result regardless of whether the hypothesis is accepted or rejected. A study with high power can accurately identify an effect or difference when one exists or vice versa.
power can be increased by increasing the sample size
what is a type 1 and type 2 error?
type I: the null hypothesis is rejected when it is true - i.e. Showing a difference between two groups when it doesn’t exist, a false positive. his is determined against a preset significance level (termed alpha).
type II: the null hypothesis is accepted when it is false - i.e. Failing to spot a difference when one really exists, a false negative. The probability of making a type II error is termed beta. It is determined by both sample size and alpha
what are the majority of brain tumours?
gliomas and metastatic disese
what are the levels of evidence?
Ia - evidence from meta-analysis of randomised controlled trials
Ib - evidence from at least one randomised controlled trial
IIa - evidence from at least one well designed controlled trial which is not randomised
IIb - evidence from at least one well designed experimental trial
III - evidence from case, correlation and comparative studies
IV - evidence from a panel of experts
what are the grading of recommendations?
Grade A - based on evidence from at least one randomised controlled trial (i.e. Ia or Ib)
Grade B - based on evidence from non-randomised controlled trials (i.e. IIa, IIb or III)
Grade C - based on evidence from a panel of experts (i.e. IV)
what form of inheritence is homocysteinuria?
auto recessive
what are the features of homocysteinuria?
often patients have fine, fair hair
Marfanoid body habitus: arachnodactyly etc
osteoporosis
kyphosis
neurological: may have learning difficulties, seizures
downwards (inferonasal) dislocation of lens
severe myopia
increased risk of arterial and venous thromboembolism
also malar flush, livedo reticularis
how is homocysteinuria investigated?
increased homocysteine levels in serum and urine
cyanide-nitroprusside test: also positive in cystinuria
how is homocysteinuria treated?
pyroxidine (vit B6)
what is fabry disease?
X-linked recessive
deficiency of alpha-galactosidase A
A. Alpha-galactosidase A normally breaks down a fatty substance called globotriaosylceramide. As a result, this fatty substance builds up in the cells of your body particularly cells lining blood vessels in the skin and cells in the kidneys, heart, and nervous system.
what are the features of fabry disease?
Features
burning pain/paraesthesia in childhood - in hands and feet
angiokeratomas - clusters of small, dark red spots on the skin
lens opacities
proteinuria
early cardiovascular disease
decreased ability to sweat (hypohidrosis);
tinnitus/ hear loss
what is the wilson and junger screening criteria?
- The condition should be an important public health problem
- There should be an acceptable treatment for patients with recognised disease
- diagnosis and treatment should be available
- There should be a recognised latent or early symptomatic stage
- The natural history of the condition should be adequately understood
- There should be a suitable test or examination
- The test or examination should be acceptable to the population
- There should be agreed policy on whom to treat
- The cost of case-finding should be economically balanced
- Case-finding should be a continuous process and not a ‘once and for all’ project
what rule can be used to work out if a disease is auto dominant/ recessive?
Autosomal recessive conditions are ‘metabolic’ - exceptions: inherited ataxias
Autosomal dominant conditions are ‘structural’ - exceptions: hyperlipidaemia type II, hypokalaemic periodic paralysis
What is the trend of risk of down sydnrome and maternal age?
20 1 in 1,500 30 1 in 800 35 1 in 270 40 1 in 100 45 1 in 50 or greater
One way of remembering this is by starting at 1/1,000 at 30 years and then dividing the denominator by 3 (i.e. 3 times more common) for every extra 5 years of age
how do majority of down syndrome cases arise?
non dysjunction
also by robertsonian translocation
what are the following HLA associated with? HLA A3 HLA B51 HLAB27 HLADQ2/8
HLA-A3
haemochromatosis
HLA-B51
Behcet’s disease
HLA-B27
ankylosing spondylitis
reactive arthritis
acute anterior uveitis
HLA-DQ2/DQ8
coeliac disease
what are the following HLA associated with?
HLADR2
HLA DR3
HLA DR4
HLA-DR2
narcolepsy
Goodpasture’s
HLA-DR3 dermatitis herpetiformis Sjogren's syndrome primary biliary cirrhosis (T1D - but stronger association with DR4)
HLA-DR4
type 1 diabetes mellitus*
rheumatoid arthritis
which enzyme is deficient in homocysteinuria?
cystathionine beta synthase
what classification is used for hypersensitivity?
Gells and coombs
what is type 1 hypersensitivity?
IgE bound mast cell
anaphylaxis
atopy
what is type 2 hypersensitivity? with examples
IgG or IgM binds to antigen on cell surface
- Autoimmune haemolytic anaemia
- ITP
- Goodpasture’s syndrome
- Pernicious anaemia
- Acute haemolytic transfusion reactions
- Rheumatic fever
- Pemphigus vulgaris / bullous pemphigoid
what is type 3 hypersensitivity ? with examples?
Free antigen and antibody (IgG, IgA) combine
- Serum sickness
- Systemic lupus erythematosus
- Post-streptococcal glomerulonephritis
- Extrinsic allergic alveolitis (especially acute phase)
what is type 4 hypersensitivity?
T-cell mediated
- Tuberculosis / tuberculin skin reaction
- Graft versus host disease
- Allergic contact dermatitis
- Scabies
- Extrinsic allergic alveolitis (especially chronic phase)
- Multiple sclerosis
- Guillain-Barre syndrome
what is type 5 hypersensitivity?
Antibodies that recognise and bind to the cell surface receptors.
This either stimulating them or blocking ligand binding
graves, myasthenia gravis etc
where does the ulnar nerve arise?
medial cord - c8, T1
what is the function of the ulnar nerve?
medial 2 lumbricals,
hypothenar muscles
flexor carpi ulnaris
interossei
sensory to medial two fingers - palmar and dorsal
what happens if ulnar nerve is damaged at
a) wrist
b) elbow
at wrist
‘claw hand’ - hyperextension of the metacarpophalangeal joints and flexion at the distal and proximal interphalangeal joints of the 4th and 5th digits
wasting and paralysis of intrinsic hand muscles (except lateral two lumbricals)
wasting and paralysis of hypothenar muscles
sensory loss to the medial 1 1/2 fingers (palmar and dorsal aspects)
Damage at elbow
as above (however, ulnar paradox - clawing is more severe in distal lesions)
radial deviation of wrist
what does troponin I , T and C bind?
troponin C: binds to calcium ions
troponin T: binds to tropomyosin,
troponin I: binds to actin to hold the troponin-tropomyosin complex in place
what is the variance?
standard deviation squared
what inhibits prolactin releasE?
dopamine e.g. cabergoline
what can increase prolactin release?
pregnancy, oestrogen, breast feeding , stress
metaclopromide
give examples of tyrosine kinase receptors…
receptor tyrosine kinase: insulin, insulin-like growth factor (IGF), epidermal growth factor (EGF)
give examples of guanyl cyclase receptors?
contain intrinsic enzyme activity
e.g. atrial natriuretic factor, brain natriuretic peptide
what are the different types of GPCRs?
Gs: Stimulates adenylate cyclase → increases cAMP → activates protein kinase A
Gi: Inhibits adenylate cyclase → decreases cAMP → inhibits protein kinase A
Gq:
Activates phospholipase C → splits PIP2 to IP3 & DAG → activates protein kinase C
what is primary hyperparathyroidism?
PTH (Elevated)
Ca2+ (Elevated)
Phosphate (Low)
Urine calcium : creatinine clearance ratio > 0.01
May be asymptomatic if mild
Most cases due to solitary adenoma (80%), multifocal disease occurs in 10-15% and parathyroid carcinoma in 1% or less
what is secondary hyperparathyroidism?
PTH (Elevated)
Ca2+ (Low or normal)
Phosphate (Elevated)
Vitamin D levels (Low)
May have few symptoms
Eventually may develop bone disease, osteitis fibrosa cystica and soft tissue calcifications
Parathyroid gland hyperplasia occurs as a result of low calcium, almost always in a setting of chronic renal failure
what is tertiary hyperparathyroidism?
Ca2+ (Normal or high)
PTH (Elevated)
Phosphate levels (Decreased or Normal)
Vitamin D (Normal or decreased) Alkaline phosphatase (Elevated) Metastatic calcification Bone pain and / or fracture Nephrolithiasis Pancreatitis Occurs as a result of ongoing hyperplasia of the parathyroid glands after correction of underlying renal disorder, hyperplasia of all 4 glands is usually the cause
what is achondroplasia?
Achondroplasia is an autosomal dominant disorder associated with short stature.
It is caused by a mutation in the fibroblast growth factor receptor 3 (FGFR-3) gene.
this results in abnormal cartilage
what are the features of achondroplasia?
short limbs (rhizomelia) with shortened fingers (brachydactyly)
large head with frontal bossing and narrow foramen magnum
midface hypoplasia with a flattened nasal bridge
‘trident’ hands
lumbar lordosis
how do majority of cases of achondroplasia occur?
random sporadic mutation
once present inherited as auto dominant
what is the main risk factor for achondroplasia?
paternal age at conception
what are the causes of acute tubular necrosis?
ischaemia - shock, sepsis
nephrotoxins - aminoglycosides, myoglobin secondary to rhabdomyolysis, radiocontrast agents and lead
what is seen in urine in acute tubular necrosis?
muddy brown casts
what are the phases of acute tubular necrosis?
oliguric phase
polyuric phase
recovery phase
what is alkaptonuria?
Alkaptonuria (ochronosis) is a rare autosomal recessive disorder of phenylalanine and tyrosine metabolism caused by a lack of the enzyme homogentisic dioxygenase (HGD) which results in a build-up of toxic homogentisic acid.
The kidneys filter the homogentisic acid (hence black urine) but eventually it accumulates in cartilage and other tissues.
what are the features of alkaptonuria?
pigmented sclera
urine turns black if left exposed to the air
intervertebral disc calcification may result in back pain
renal stones
how is alkaptonuria managed?
high-dose vitamin C
dietary restriction of phenylalanine and tyrosine
what are the functions of vit C?
antioxidant
collagen synthesis: acts as a cofactor for enzymes that are required for the hydroxylation proline and lysine in the synthesis of collagen
facilitates iron absorption
cofactor for norepinephrine synthesis
how does vit C deficiency present?
gingivitis, loose teeth poor wound healing bleeding from gums, haematuria, epistaxis general malaise Follicular hyperkeratosis and perifollicular haemorrhage Ecchymosis, easy bruising Sjogren's syndrome Arthralgia Oedema
describe the location of the following dermatomes C2 C3 C4 C5
C2 Posterior half of the skull (cap)
C3 High turtleneck shirt
C4 Low-collar shirt
C5 Ventral axial line of upper limb
describe the location of the following dermatomes C6 C7 C8 T1 T2
C6 Thumb + index finger C7 Middle finger + palm of hand C8/ T1 Ring + little finger T1 - inner lower arm T2 - inner upper arm
describe the location of the following dermatomes T4/5 T10 L1 L4 L5
T4/5 nipple T10 - belly button L1 Inguinal ligament L4 Knee caps L5 Big toe, dorsum of foot (except lateral aspect)
describe the location of the following dermatomes
S1
S2/3
S1 lateral foot
S2/3 - genitals
what is meant by incidence and prevalence?
The incidence is the number of new cases per population in a given time period.
The prevalence is the total number of cases per population at a particular point in time
prevalence = incidence * duration of condition
in chronic diseases the prevalence is much greater than the incidence
what are the 5 principles of mental capacity act?
assumed to have capacity unless it is established that he lacks capacity
not to be treated as unable to make a decision unless all practicable steps to help him
not to be treated as unable to make a decision merely because he makes an unwise decision
An act done, or decision made,for a person who lacks capacity must in his best interests
Before the act is done regard to whether the purpose for which it is needed can be as effectively achieved in a way that is less restrictive of the person’s rights and freedom of action
what is the difference between prostacyclins and thromboxane?
thromboxane - platelet aggregation and vasoconstriction
prostacyclins - vasodilation and reduced platelet aggregation
what is atrial natureitic peptide?
secreted mainly from myocytes of right atrium and ventricle in response to increased blood volume
secreted by both the right and left atria (right»_space; left)
natriuretic, i.e. promotes excretion of sodium
lowers BP
antagonises actions of angiotensin II, aldosterone
what is meant by non-penetrance?
lack of clinical signs and symptoms (normal phenotype) despite abnormal gene.
All of the following conditions follow which type of inheritance?
Acute intermittent porphyria Ehlers-Danlos syndrome Hereditary spherocytosis Hyperlipidaemia type II Hypokalaemic periodic paralysis Marfan's syndromes Myotonic dystrophy Neurofibromatosis Noonan syndrome Osteogenesis imperfecta Peutz-Jeghers syndrome tuberous sclerosis
auto dominant
what is selection bias?
Error in assigning individuals to groups leading to differences which may influence the outcome.
e.g. sampling bias , non-responder bias, healthy worker effect
what is recall bias?
Difference in the accuracy of the recollections retrieved by study participants, possibly due to whether they have disorder or not. E.g. a patient with lung cancer may search their memories more thoroughly for a history of asbestos exposure than someone in the control group. A particular problem in case-control studies.
what is publication bias?
Failure to publish results from valid studies, often as they showed a negative or uninteresting result. Important in meta-analyses where studies showing negative results may be excluded.
what is expectation bias?
Only a problem in non-blinded trials. Observers may subconsciously measure or report data in a way that favours the expected study outcome.
what is the hawthorne effect?
Describes a group changing it’s behaviour due to the knowledge that it is being studied
what is lead time bias?
Occurs when two tests for a disease are compared, the new test diagnoses the disease earlier, but there is no effect on the outcome of the disease
what is the origin of the brachial plexus?
anterior rami of C5-T1
in terms of location, where doadult tumours lie in comparison to childhood tumours
the majority of adult tumours are supratentorial, where as the majority of childhood tumours are infratentorial.
which tumours metastasise to the brain?
lung (most common) breast bowel skin (namely melanoma) kidney
what is the most common primary tumour of the brain? what is the prognosis?
Glioblastoma
poor prognosis - around 1 year
how does glioblastoma present on imaging and histologically
On imaging they are solid tumours with central necrosis and a rim that enhances with contrast. Disruption of the blood-brain barrier and therefore are associated with vasogenic oedema.
Histology: Pleomorphic tumour cells border necrotic areas
what is the second most common brain tumour in adults (after glioblastoma)? what is their prognosis like?
meningioma
Meningiomas are typically benign, extrinsic tumours of the central nervous system. They arise from the dura mater of the meninges and cause symptoms by compression rather than invasion.
where do majority of meningiomas form?
they typically are located at the falx cerebri, superior sagittal sinus, convexity or skull base.
how do meningiomas present histologically?
Spindle cells in concentric whorls and calcified psammoma bodies