11 Clinical biostatistics

MNJ11-001
** May 2013:

images/MNJ-P-OSCE 11. Clinical biostatistics_page_4_Figure_8.jpeg

What is name of this plot?
What is the arrowed figure named as?
In given studies, which study shown in best association in view of outcome?
Where is this plot used in medical research

Answer

No model answer in source material.

MNJ11-002
You are doing a study is "acupuncture better for depression than medicine". And the result are like this:

cupuncture		Medication	1
ment	N _A	Improvement	$N_{M}$
	27	6	20

Calculate the odds ratio
What is its significance in a study?

Answer

No model answer in source material.

MNJ11-003
In an area the under-5 mortality is 8/1000 live births:

Calculate the child survival index in that area and also write down formula for child survival\nindex.

| 154 OSCE Clinical Pediatrics

oO.

images/MNJ-P-OSCE 11. Clinical biostatistics_page_5_Picture_7.jpeg

Write down formula of meidence, prevalence and stillbirth rate.
Write down formula for case fatality rate, attack rate and secondary attack rate.
Whats the name of this plot?
What 1s its use in medical research?
Describe the following points in this plot (points—A and B, B1).

Answer

No model answer in source material.

MNJ11-004
** The following is a table which shows cigarette smoking and lung cancer:

Cigarette smoking	Developed cancer	Did not develop cancer
Yes	70	6930
No	2	2997

Calculate the relative risk.
What 1s value of relative risk in medical research?

Answer

No model answer in source material.

MNJ11-005
* On auditing urine growth, following were the result:

Urine microscopy	Pure growth	Multiple growth
>50 WBC	95(A)	15(B)
<50 WBC	10(C)	200(D)

Calculate positive predictive value of urine microscopy
Calculate negative predictive value of urine microscopy.
Calculate sensitivity and specificity

Answer

No model answer in source material.

MNJ11-006
**

images/MNJ-P-OSCE 11. Clinical biostatistics_page_6_Picture_2.jpeg

Define median, 1st quartile and 3rd quartile.
Define rate and ratio What 1s difference in these two?
Whats the difference in "Case control" and "Cohort" study design
What is the difference between incidence and prevalence?

Answer

No model answer in source material.

MNJ11-007
** Calculate the mean, median, mode, mean deviation and SD of the diastolic pressures given below:

83,75, 81,79, 71,95, 75, 77, 84,71, 75, 75, 77,79, 81, 83, 84, 95.

Answer

No model answer in source material.

MNJ11-008
A.**

images/MNJ-P-OSCE 11. Clinical biostatistics_page_6_Figure_9.jpeg

What is name of curve?
What are uses?
What does it represent?

Answer

No model answer in source material.

MNJ11-009
B. Station

OSCE Clinical Pediatrics

156

images/MNJ-P-OSCE 11. Clinical biostatistics_page_6_Figure_13.jpeg

What is name of curve?
What are uses?

Answer

No model answer in source material.

MNJ11-010
During a study at hospital the PEFR of 100 adolescences boys follow a normal distribution with a mean of 280 lit/min, standard deviation 30 lit/min and standard error of 2 lit/min.

What will be the range in which 95% of the boys PEFR will lie in the sample?
What will be the range in which mean PEFR of the population will lie from which the sample was taken?

Answer

No model answer in source material.

MNJ11-011
A study was carried out to assess the utility of IgM ELISA test in the diagnosis of leptospirosis. Blood culture positive cases were considered the gold standard for diagnosis. A total of 100 cases were studied.

Leptospira were grown in blood culture in 40 of these cases. IgM ELISA was positive in 70 out of 100 cases. Out of these 70 cases, Leptospira were cultured in 30. IgM ELISA was negative in 30 cases, out of this 30, Leptospira was grown in culture in 10 cases.

Calculate the following for IgM ELISA as a diagnostic test for leptospirosis.

Specificity
Sensitivity
Positive predictive value
Negative predictive value

Answer

No model answer in source material.

MNJ11-012
A new rapid test was compared with the gold standard of blood culture for diagnosing enteric fever. Of total 500 fever cases, culture was positive in 400 children. Rapid test was positive in 300 children and both culture and rapid test were positive in 260 children.

a. Sensitivity
b. Specificity
c. Positive predictive value
d Negative predictive value
e Likelihood ratio positive
f. Likelihood ratio negative

Calculate the following for the rapid test:
a. Sensitivity
b. Specificity
c. Positive predictive value
f. Likelihood ratio negative

Answer

No model answer in source material.

MNJ11-013
Write following journal article in Vancouver style.

Article: Hand grip strength and its relationship with birth weight in adolescent population

Authors: Bhargava S, Sharma M and Kalra E

Journal. Indian Pediatrics: Year 2013, volume 78, page 301-305

Answer

No model answer in source material.

MNJ11-014
Yearly data (for year 2000) pertaining to deliveries and their outcome in a community is as follows:

No of total births 10000

No. of stillbirths: 80

No. of preterm deliveries: 1500

No. of newborn deaths

In first week of life: 320

During 2-4 weeks of life: 180

No. of deaths during first year of life: 500

Calculate perinatal and neonatal mortality rates for this community, demonstrating the steps taken to arrive at the results.

images/MNJ-P-OSCE 11. Clinical biostatistics_page_8_Picture_2.jpeg

Answer

No model answer in source material.

MNJ11-015
Match the following:

Level of evidence	Characteristics
I	Case series
П	Lesser quality RCT (e.g. <30% follow up; no blinding; improper randomization/systematic review of level II RCT)
Ш	Expert opinion
IV	High quality RCT with statistically significant difference or no statistically significant difference but narroconfidence interval/systematic review of level I RCT
V	Case control study, observational, retrospective compara- tive study/systematic review of level III RCT

Answer

No model answer in source material.

MNJ11-016
Determine the sample size to find out the vitamin A requirement in the under five children of Pune district. From the existing literature the mean daily requirement of the same was documented as 930 I.U. with a SD of 90 IU. Consider the precision as 9.

Answer

No model answer in source material.

MNJ11-017
The peak flow rates of 10 children of same age are as follows:

250, 260, 290, 200, 240, 240, 260, 270, 270, 290

What is the range?
What is the mean deviation and mean?
What is the standard deviation?

Answer

No model answer in source material.

MNJ11-018

ANSWERS

Ans. 1. 1. Forest plot 2. Diamond 3 Study by Kalyan 4. Meta-analysis
Ans. 2. 1. OR = $\frac{n (Exposed)}{n (Non-exposed)}$

= \frac{12 / 15}{6 / 14} = 1.86 to 19

Outcome variable is 1 9 times more in the acupuncture group than in the medicine group.
Ans. 3. 1. Child survival index = $\frac{1000 under 5 mortality}{10}$

= \frac{1000 - 8}{10} = 99.2

Prevalence =

\frac{Number of old + new cases}{Population at given time} \times 100

Stillbirth date =

\frac{Number of fetal deaths (with weight > 1000 g)}{Total live + stillbirths (with weight > 1000 g)} \times 1000

A t t a c k r a t e = \frac{N u m b e r o f c a s e s i n a y e a r o f a d i s e a s e}{N u m b e r o f p o p u l a t i o n a t r i s k f o r t h e s a m e d i s e a s e}

$S e c o n d a r y a t t a c k r a t e = \frac{S e c o n d a r y c a s e s}{N u m b e r o f s u s c e p t i b l e p e r s o n c a m e i n c o n t r a c t}$

Ans. 4. 1. Box-and-whisker plot
- They display a statistical summary of a variable: Median, quartiles, range and possibly extreme values.
  - The central box represents the values from the lower to upper quartile (25– 75 percentile).
- 1. A The middle line represents the median.
  - B. 25 quartile

B1-75 quartile

Ans. 5. 1. RR = Incidence of disease in exposed/incidence of disease in non-exposed

Incidence of disease in exposed =

\frac{70}{7000}

= 10 per 1000

So RR =

\frac{10}{1}

= 10

Ans.6. 1. PPV = True positive /true positive + false positive

\frac{95}{(95 + 15)} = 86.3 %

\frac{200}{(200 + 10)} = 95.2 %

\frac{A}{A + C} = \frac{95}{105}

Specificity =

\frac{D}{D + B} = \frac{200}{215}

Ans. 7. 1. If the observations are arranged in ascending or descending order Median: 50% observations are below and 50% above this value Ist quartile: 25% observations are below and 75% above this value ard quartile: 75% observahons are below and 25% above this value
- . Rate: Numerator 1s part of denominator Ratio' Numerator is not part of denominator
- . Case control study is retrospective and cohort study is prospective
- . Incidence: The number of new cases occuring in defined population during a specified period of time Prevalence: Number of all cases old or new ata given point of time or over a period

Ans.8. Mean=80 Median=79 Mode=75 MDandSD= Value

Ans. 9A.1. A receiver operating characteristic (ROC) curve.

of time ma given population

Zz: ROC analysis provides tools to select possibly optimal models and to discard suboptimal ones.
. It is a graphical plot of the sensitivity, or true positive rate, versus false positive rate (1-specificity or 1-true negative rate), for a binary classifier system as 1ts discrimination threshold is varied.

A scatter plot chart

. It displays series as a set of points specified by x and y coordinates A scatter plot 1s useful for showing nonlinear relationships between variables. It requires at least one category and two series (representing the x and y coordinates).

Range in which 95% of girls PEFR in the sample will lie Mean +/-2SD = 280 + /—2(30) = 220 - 340

. Range in which mean PEFR value will lie: Mean + /-2SE (standard error) 95% Confidence interval = 280 + /—-2(2) = 276-284

Ans. 11.

	Blood c/s+	Blood cfs—
IgM ELISA +	30(a)	40(b)	70
IgM ELISA -	10(c)	20(d)	30

Specificity:

\frac{d}{d + b} \times 100

, $\frac{20}{20 + 40} \times 100 = 33.3 %$

Sensitivity:

\frac{a}{a + c} \times 100

, $\frac{30}{30 + 10} \times 100 = 75 %$

\frac{a}{a + b} \times 100

, $\frac{30}{30 + 40} \times 100 = 42.85 %$

\frac{d}{c + d} \times 100

, $\frac{20}{10 + 20} \times 100 = 66.6 %$

Ans. 12.

	Culture positive	Culture positive
Rapid test positive	260(a)	40(b)	300(a+b): Test positive
Rapid test negative	140(c)	60(d)	200(c+d): Test negative
Total	400: Disease positive	100: Disease negative 500: Total

* Sensitivity: a/a + c = 260/400 = 65%
* Positive predictive value: a/a + b = 260/300 = 87%
* Negative predictive value: d/c + d = 60/200 = 30%
* Likelihood ratio positive = sensitivity /1-spectficity = 0.65/0.4 = 1.625
* Likelihood ratio negative = 1-sensitivity / specificity = 0.35/0.6 = 0.58

Ans. 13. Author's surname initials. Title of Article, Title of Journal [abbreviated] Year of Publication, Month and Date, Volume Number (Issue Number): Page numbers.

* Bhargava 5S, Sharma M and Kalra E. Hand grip strength and its relationship with birth weight in adolescent population. Indian Pediatr. 2013; 78: 301-5.

Ans. 14.1. Perinatal mortality rate:

= \frac{80 + 320}{10, 000} \times 1, 000

= 40 per 1000 live births.

= \frac{320 + 180}{10, 000} \times 1000

= 50 per 1000 live births.

Ans. 15.

Level of evidence	Characteristics
I	High quality RCT with statistically significant difference or no statistically significant difference but narrow confidence interval/ systematic review of level IRCT
II	Lesser quality RCT (e.g. <30% follow-up; no blinding; improper randomization) /systematic review of level II RCT
ll	Case control study, observational, retrospective compara tive study/systematic review of level II] RCT
IV	Case series
Vv	Expert opinion

Ans. 16.

N = 4 S D^{2} / L^{2}

$\frac{4 \times 90 \times 90}{9 \times 9} = 400$

Ans. 17.1. 200 to 290

\frac{\sum (x - \overset{―}{x})}{N}

Mean: 257, mean deviation: 19.8

σ = \sqrt{\frac{\sum (x - \overset{―}{x})^{2}}{N}}

N when sample size >30

(N-1) when sample size <30

* Take the deviation of each value from mean (x—x)
* Square each (x=x)?
* Add and squared deviation E ( x-x)?
* Divide by no. of observation or n 1 if <30
* Then take square root

Ans. 18. 1. Scatter diagram and correlations.

C Strong positive correlation D Weak negative correlation

E. Strong negative correlation F Perfect correlation

images/MNJ-P-OSCE 11. Clinical biostatistics_page_8_Figure_15.jpeg

Identify diagram.
What are the uses?
Name each components A to F along with interpretation of each
A The middle line represents the median.
b. 25 quartile
Ascatter diagram is a tool for analyzing relationships between two variables One variable 1s plotted on the horizontal axis and the other is plotted on the vertical axis. The pattern of their mtersecting points can graphically show relationship patterns

Answer

No model answer in source material.