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In its most general sense, what is a biomarker used for?
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To infer or predict an otherwise unmeasurable biological state
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Systems biology
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Using biomarkers to understand the mechanisms of disease, drug resistance, progression and prognosis
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What affects whether or not a biomarker will be used for clinical purposes?
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Often logistical considerations like money and whether or not cost is balanced by benefit
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Sensitivity =
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# tested positives (and are actually positive) /#ppl actually positive
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Specificity =
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# tested negatives (and are actually negative) /# ppl actually negative
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Can you have a test for a biomarker that is both highly specific and sensitive?
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It is very rare, usually if you have a test that is very sensitive you need a low threshold and often this means more false positives
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What are the most important values conveying the efficacy of test to people in teh clinic
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Positive predictive value and Negative predictive value
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PPV =
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# ppl positive/ # ppl diagnosed positive
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NPV =
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# ppl negative/ # ppl diagnosed negative
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Why are biomarkers bad for large scale screening of rare diseases?
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Because of the low prevalence and poor positive predictive values and even highly specific tests can have poor PPV
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2 dimensional SDS-PAGE gels give a global view of ___
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Protein abundance
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Mass spectrometry identifies ______ by ____
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Proteins by Peptide Mass Fingerprinting
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Tandem mass spectrometry has what benefit?
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Direct peptide sequence characterization
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How do you do a 2d gel (isoelectric focusing)
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1. run a gel that separates proteins based on pI2. use the bands of that gel to run one that separates by size and charge
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How is mass spec performed (in the machine only)
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1. the sample is ionized 2. the sample enters an electric field that spreads them based on mass to charge ratio (a mass analyzer)3. they enter the detector where they're counted
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