Chemistry Flashcards
What is the cause of deep yellow urine with yellow FOAM?
BILIRUBIN
foam can also occur in proteinuria
What compound in urine can cause red or orange color and has fluorescence with UV light (360nm)?
Seen in Porphyria ( Uroporphyrin and coproporphyrin )
Abnormal urine odors and associations:
Fruity or sweet: ketoacidosis, starvation
Mousy or musty: phenylketonuria
Fishy: UTI with proteus, tyrosinemia
Ammoniacal: UTI with E. coli, old standing urine
Foul odor: UTI
Rancid: Tyrosinemia
Sweaty feet: Isovaleric acedemia
Maple syrup or burnt sugar: maple syrup urine disease
Name the type of renal calculus that is formed in acid urine ?
- Uric acid calculi
Examples of PRE-RENAL or overflow proteinuria?
When concentration of LMW proteins increase in plasma it overflows into urine…
Ig light chains or BJ proteins - plasma cell dyscrasias
Hemoglobin- intravascular hemolysis
Myoglobin- skeletal muscle trauma
Lysozyme - AML M4 or M5
The majority of the body magnesium stores are found in which tissues?
50-60% bone
40-50% soft tissue and 1% EC fluid
During phlebotomy, which of the following is affected by posture, showing a higher reading on standing than supine ?
Plasma renin
peaks on standing and falls with supine position
Thoracentesis with milky fluid and triglyceride level of 75mg/dL. Next best step in management ….
Triglyceride > 110 mg/dL - chylothorax
TG < 50 mg/dL - excludes a chylothorax
If level is between 50 and 110 - do LIPOPROTEIN ELECTROPHORESIS to determine if chylomicrons are present
Which one of the following tests is the best statistical test to determine if the null hypothesis is correct in stating that no significant difference exists between the variance for two study groups ?
F- test ( aka: variance ratio test) is used to determine if standard deviations of two data sets are statistically different.
ROC curve axis (x, y) represent
Y axis: true positive rate or sensitivity
X axis: false positive rate (100-specificity) or rarely specificity
Screening test - HIGH sensitivity
Confirmatory year- HIGH specificity
Statistical tests and what they test :
T- test
Chi- square
Kolmogorov-Smirnov
F-test
T- test : 2 set of observations are significantly different
Chi- square: evaluates differences in proportion between 2 groups
Kolmogorov-Smirnov : to see if a set of data follows a Gaussian distribution
F-test : compares standard deviation
CLSI standards for reference ranges and intervals:
- To see if ref range is POPULATION appropriate- test 20 individuals, if no more than 2 are outside the published ref interval, test is validated. If > 2, second set of 20 to be tested.
- To achieve statistical reliability to DETERMINE LIMITS for reference interval, 120 individuals must be tested. Data to be inspected for outliers , and calculations repeated excluding outliers.
What is unique about upper reference limits for glucose and total cholesterol tests
Based on outcomes data, upper reference limit was set at the point where risk of subsequent disease manifestations ( DM complications, CAD) began to increase
For which tests are reference intervals derived as the central 95% of results from apparently healthy individuals insensitive to disease- induced changes in a patient?
Alkaline phosphate
Calcium
Free thyroxine
For these, the results within a person are kept within extremely narrow limits, while varying considerably from one person to the next . Hence population based ref limits are insensitive. CENTRAL 95% of results are used as ref ranges instead of mean +- 2SDs.
Which tube should be filled LAST during phlebotomy?
Per CLSI, Blood culture first Plain tubes Coag ( Na citrate) tubes Serum separator tubes Tubes with additives
