NEXT-NEET PG/FMGE/INICET/CMS ( MCQ pratice, discussion, tricks and tips)

Let's understand Cut off value- 126 Distribution of subjects between 110 to 140 Some disease patients would have sugar level 110 to 125, in these at Cut off 126, test would be negative ( false negative) So if now Cut off value decrease 126 to 110 , these all comes positive ( false negative decreased, eventually sensitivity and NPV increased) Some non- diseased persons would have FBG level 110 to 125, these subjects would have negative test results at Cut off value 126( true negative) But now at Cut off value 110, all these would be positive ( false positive) So number of false positive increased,  eventually specifivity and PPV decreased In summary, if cut off value decreased- False negative decrease False positive increases Sensitivity increases Specifivity decreased NPV increases PPV decreased True positivity rate (Sensitivity) increases True  negative rate (specifivity) Decreased Diseased persons comes more positive (previously false negative becomes true postive) Non- Diseased persons comes more…

Hepatitis B Antibody after vaccination- anti HBs ( surface) Antibody after natural infections Both anti HBs and anti HBc

Multiple test sequence Parallel All test applied simultaneously Disease positive- any single test positive Disease negative- all test should be negative It will decrease false negative ( as Multiple test applied,  Disease person likely to get any test positive) At the same time false positive rate increases ( non Disease person likely to get any positive result) So here False negative decrease False positive increases Eventually Sensitivity and NPV - increases Specifivity and PPV- decrease Series testing Multiple test applied in sequelae Next test only applied to only positive in first test and so on Disease positive- all test should be positive Disease negative- any one test negative Here False positive decrease False negative increases Specifivity and PPV - increases Sensitivity and NPV - decrease ( opposite to Parallel testing) To confirm a diagnosis more surely Specifivity should be more ( less false positive rate and more true negative rate) So testing should be done in series Reducing…