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Q) To Study the effect of an antiviral drug, we note down the initial viral load and then after a month repeat viral load. What is the the most appropriate statistical test of significance to test the change in viral load
(a) Paired t-test (b) Unpaired or independent t-test (c) Analysis of variance (d) Chi-square test
Ans a) Paired t test
paired t test is used When comparing the same person results after giving a drug or doing a surgery or any intervention
A paired t-test is used when we are interested in the difference between two variables for the same subject. Often the two variables are separated by time
Unpaired t test
The unpaired two-samples t-test is used to compare the mean of two independent groups.
For example, suppose that we have measured the weight of 100 individuals: 50 women (group A) and 50 men (group B). We want to know if the mean weight of women is significantly different from that of men In this case, we have two unrelated (i.e., independent or unpaired) groups of samples. Therefore, it’s possible to use an independent t-test to evaluate whether the means are different.
The basic idea behind the test is to compare the observed values in your data to the expected values that you would see if the null hypothesis is true.
To determine whether the association between two qualitative variables is statistically significant
Analysis of Variance ANOVA example
A group of psychiatric patients are trying three different therapies: counseling, medication and biofeedback. You want to see if one therapy is better than the others.
Q) An young male with cholangitis, EHPVO + Portal Biliopathy was drained with a plastic biliary stent next step?
a) Repeat biliary Stenting every 3 months then followed up
b) Replace plastic to bare metal stent
c) Prepare for Lineorenal shunt surgery
d) Do MRCP and proceed accordingly
Points about Portal Biliopathy
Portal biliopathy (PB) is a clinical condition defined as the presence of abnormalities in the biliary tree (including biliary tree and gallbladder) in patients with non-cirrhotic/non-neoplastic extrahepatic portal vein obstruction (EHPVO) and portal cavernoma.
The spectrum of biliary abnormalities include both intra- and extra-hepatic biliary stenosis (single or multiple)
With or without consensual above dilation
Bile duct wall irregularity or thickening
Bile duct angulation
Varicose veins located at the ductular walls and gallbladder
a) ALPPS should not be considered in every patient in whom PVE has failed.
b) CT scan and volumetric assessment is done after POD 7 and proceeded to stage 2 if sFLR greater than 30% (BWR > 0.5%) or 40% (BWR > 0.8%) depending on parenchymal quality
c) Indicated for Large CRLM
d) Is a relative contraindication for patients with hilar cholangiocarcinoma
Ans a) ALPPS should be considered in every patient in whom PVE or the classic two-stage approach is not feasible or has failed
The limits for safe hepatic resections are usually considered from 20% to 40%, depending on the quality of liver parenchyma (fibrosis, steatosis,
chemotherapy-related liver injury). The lower limit for FLRV is set at 20% in patients with normal livers, 30% to 35% in patients with chemotherapy-related liver injury, and 40% in patients with chronic liver disease
Cut-off values for proceeding to stage 2, usually after 7 to 14 days, are sFLR greater than 30% (BWR > 0.5%) or 40% (BWR > 0.8%) depending on parenchymal quality. ( Ref BG page 1665)
Currently,CRLM is the most promising indication, especially for bilobar involvement
In hilar cholangiocarcinoma its a relative contraindication as the mortality and morbidity are high