Week 10 Lab tests Flashcards
Diurnal variation of cortisol
High in the morning
Low in the eveing
Diurnal variation of testosterone
High in the morning (taken in ithe morning)
complication with venous stasis and tests
Venous stasis while taking blood:
Albumin may increase which lead s to the increase of calcium.
Gaussian/symmetrical – frequency vs measurement (SD significance)
1 SD is 67%
2 SD is 95%
What sort of distribution does TSH have (Thyroid stimulating hormone)
skewed distribution, a longer tail at the higher range.
Bias (high precision but slightly inaccurate)
shift population curve
false negatives in tests
When people have disease but sit in reference range
false positives in tests
when well people sit in the abnormal/disease range.
including full reference population leads to…
High specificity (few false positive)
BUT:
Low sensitivity (many false negatives)
cut offs for rare disorders
can no longer use 95% interval. Have to have excellent specificity (no disease?) and sensitivity (disease?)
Serious hyperkalaemia and hypocalcaemia??
- extra potassium from the EDTA can artificially increase the potassium concentration in the sample
- If a serum sample is contaminated with K+ EDTA, the EDTA will bind to calcium in the sample, artificially lowering the measurable calcium level.
Order of blood draw
Do the biochemistry first, no contamination (plain serum)
Immunoassay results can be interefered by?
autoimmune antibodies that target exogenous things.
False positive immunoassay results
heterophilic antibodies and labelled antibodies form complex without antigen
False negative immunoassay results
steric hindrance from heterophilic antibodies that block antigen and labelled antibody complex.
