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A 15 year old boy presented with wheezing when playing football and nocturnal cough.

Which is the best test to confirm the underlying condition?

Available marks are shown in brackets

1 ) A trial of oral corticosteroids [0]

2 ) A trial of inhaled corticosteroids [0]

3 ) A trial of inhaled salbutamol [0]

4 ) Serial peak expiratory flow rate measurements [100]

5 ) Spirometry alone [0]

Comments:

Demonstration of variable obstruction of the airways provides good evidence for asthma, with itscharacteristic morning dips. Failure to respond to bronchodilator therapy does not exclude asthma asresponse may be small in children, and in adults with persistent or more severe asthma. Those who failto respond to inhaled bronchodilator require a steroid trial (either 4 weeks of high dose inhaled steroids or2 weeks of oral Prednisolone).

In a study of a new drug for asthma, a researcher wishes to compare average serum drug concentrationsin volunteers, four hours after taking the drug;

in the fasting state then

after a meal

Which of the following would be the most appropriate statistical test to use?


1 ) chi-squared test [0]

2 ) Pearson's correlation coefficient [0]

3 ) Student's paired t-test [100]

4 ) Student's unpaired t-test [0]

5 ) Wilcoxon test [0]

Comments:In this scenario we are dealing with use of the drug in the same volunteers with the intervention being theeffect of feeding on drug concentrations. Thus you'll be comparing means in the same subjects and thepaired t-test would be the most appropriate test. Go here for more statistical info.

Which of the following statements is true of the pulmonary function test's vital capacity (VC)?


1 ) Vital capacity cannot be measured from spirometry alone [0]

2 ) Vital capacity is increased in emphysema and reduced in interstitial fibrosis [0]

3 ) Vital capacity is the maximal amount of air which can be exhaled after maximal inspiration [100]

4 ) Vital capacity is the sum of tidal volume (VT) and inspiratory capacity (IC) [0]

5 ) Vital capacity, when reduced, is a specific indication of restrictive lung disease

A 7 month old boy is presented to a doctor by his parents with symptoms of reccurent upper respiratorytract infections. No other members of the family suffer from any smiliar infections.Physical examination
http://www.onexamination.com/site/Paedia.asp?id=918http://www.onexamination.com/site/Paedia.asp?id=918http://www.onexamination.com/site/Paedia.asp?id=918


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showed mild facial hypoplasia. Biochemistry investigations revealed hypocalcaemia. Microbiologicalinvestigations were normal and immunoglobulins were within normal limits. The infants immune functionwould show the following deficiency:


1 ) Complement Deficieny [0]

2 ) B cell number and function [0]

3 ) T cell number and function [100]

4 ) Plasma Cell [0]

5 ) Macrophage number and function [0]

Comments:This child suffers from DiGeorges syndrome. Patients with DiGeorges Syndrome often have near normallevels of immunoglobulins but with significant decreases in T cell numbers and relative increase in thepercentage of B cells.

An 18 year-old female is admitted with a depression of her conscious level. Arterial blood gas analysisrevealed:

pH 7.26

pO2 12.1 kPa

pC02 3.9 kPa

standard bicarbonate 14.7 mmol/L

Which one of the following would account for these results?


1 ) Analytical error [0]

2 ) Metabolic acidosis [100]

3 ) Persistent vomiting [0]

4 ) Respiratory acidosis [0]

5 ) Respiratory alkalosis [0]

Comments:This patient has a metabolic acidosis with an effort at respiratoty compensation as reflected by elevatedpO2 and reduced pCO2. This could be due to poisoning or a condition such as Diabetic ketoacidosis.Vomiting would cause a metabolic alkalosis.

An 18-year-old boy is suspected of having cystic fibrosis. Which of the following results would be mostsuggestive of this condition?


1 ) Abnormal pancreatic function tests [0]

2 ) Abnormalities in lung function tests [0]

3 ) Bronchiectasis on a chest x-ray [0]

4 ) Elevated sweat chloride concentration [100]

5 ) Low immunoreactive plasma trypsinogen [0]

Comments:
http://www.onexamination.com/site/Paedia.asp?id=918http://research.med.umkc.edu/tlwbiostats/sens_specif_predval.html


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The sweat test is the most important test for CF. Up to 99% of children with CF have sweat chloride andsodium levels above 70 and 60 mM respectively. In normal children, sweat sodium is higher thanchloride. The reversed ratio is another pointer to CF. Two sweat tests should be performedspontaneously on both arms with pilocarpine iontophoresis. Older children with CF and pancreaticinsufficiency have low immunoreactive trypsin. This and the other tests mentioned may be suggestive ofCF but are not diagnostic.

A new publication describes a new test for cystic fibrosis. You want to know what proportion of patientswith cystic fibrosis who would be correctly identified by this new test. Which one of the following valueswould identify this?


1 ) accuracy [0]

2 ) negative predictive value [0]

3 ) positive predictive value [0]

4 ) sensitivity [100]

5 ) specificity [0]

Comments:

The proportion of patients with the disease who would be identified by the new test is the specificity. Thisrefers to the proportion with the disease who truly have cystic fibrosis and are identified as such by thetest. Positive predictive value refers to the percent of people having a positive test who actually have thedisease interpreted in conjunction to the prevalence of the disease (True positives/True positives+Falsenegatives).

A new publication describes a new test for cystic fibrosis. You want to know what proportion of patientswith cystic fibrosis would be correctly identified by this new test. Which one of the following values wouldidentify this?


1 ) accuracy [0]

2 ) negative predictive value [0]

3 ) positive predictive value [0]

4 ) sensitivity [100]

5 ) specificity [0]

Comments:The proportion of patients with the disease who would be correctly identified by the new test is thesensitivity. This refers to the proportion with the disease who truly have cystic fibrosis and are identifiedas such by the test. Positive predictive value refers to the percent of people having a positive test whoactually have the disease interpreted in conjunction to the prevalence of the disease (True positives/Truepositives+False negatives).

Sensitivity Specificity and redictiveValues


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ssoci tion of symptoms or test results nd dise seClinical research often investigates the statistical relationship between symptoms

(or test results) and the presence of disease. Chi-square analysis can be applied

to the data in the form of a 2 by 2 table in order to assess the statistical

significance of the association between the presence or absence of a symptom

and the presence or absence of the disease under study. When significant

associations are found, it is useful to express the data in ways which are clinically

relevant. In order to communicate the results in a consistent manner, the

following definitions have been developed.Test Result

Negative Posit ive

a b

absent 8660 960

disease c d

present 40 340

Sensitivity

the probability that a symptom is present (or screening test is positive) given thatthe person has the disease d/(c+d) 340 / (40+340) = .895. This is also know as the

true positive rate.

Specificitythe probability that a symptom is not present (or screening test is negative) given

that the person does not have the disease a/(a + b) 8660 / (8660 + 960) = .90. This

is also known as true negative rate.

Predictive value positivethe probability that a person has the disease given a positive test result d / (b + d)

340 / (960+340) = .26

Predictive value negative

the probability that a person does not have the disease given a negative test a / (a+ c) 8660 / (8660+40) = .995

False negativea person who tests as negative but who is actually positive

False positivea person who tests as positive but who is actually negative

In a study of a new drug for asthma, a researcher wishes to compare average serum drug concentrations


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in volunteers, four hours after taking the drug; a. in the fasting state then b. after a meal. Which of thefollowing would be the most appropriate statistical test to use?


1 ) chi-squared test [0]

2 ) Pearsons correlation coefficient [0]

3 ) Students paired t-test [100]

4 ) Students unpaired t-test [0]

5 ) Wilcoxon test [0]

Comments:In this scenario we are dealing with use of the drug in the same volunteers with the intervention being theeffect of feeding on drug concentrations. Thus youll be comparing means in the same subjects and thepaired t-test would be the most appropriate test. Go here for more statistical info

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