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Tim's CP Board Review > Chemistry > Flashcards

Chemistry Flashcards

1
Q

Anion gap calculation

A

Na - Cl - HCO3

Should not exceed 12 normally

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2
Q

Osmotic gap calculation

A

2Na + BUN/3 + Glucose/20

Should not exceed 10 normally

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3
Q

Ketones in DKA

A

About 80% are beta-hydroxybutyrate, which is not detected by nitroprusside technique. Converted to acetoacetate/acetone which are detected (may have transient increase with treatment)

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4
Q

Causes of anion-gap metabolic acidosis

A 
Methanol
Uremia
Diabetic ketoacidosis
Propylene glycol
Isoniazid
Lactate
Ethanol
Salicylates
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5
Q

Causes of non-anion-gap metabolic acidosis

A

Bicarbonate losses (diarrhea, renal tubular acidosis)

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6
Q

Water distribution

A

TBW is 60% water
2/3 of water is intracellular, 1/3 is extracellular
1/4 of extracellular water is intravascular (1/12 overall)

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7
Q

Pseudohyponatremia

A

Spurious hyponatremia seen on indirect ISE methods where an assumed 93% water content is incorrect in the settings of patient hyperlipidemia or paraproteinemia.

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8
Q

FENa

A

(Urine sodium * Plasma creatinine) / (Urine creatinine * plasma sodium)

If low (1%), reabsorption is functional.

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9
Q

Causes of hypernatremia

A

Almost always dehydration or diabetes insipidus

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10
Q

Causes of hyponatremia

A

Overhydration, SIADH

Wasting states (nephrotic syndrome, cirrhosis)

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11
Q

Pseudohyperkalemia

A

Can be caused by hemolysis, collection into EDTA tube, clenching during phlebotomy or small needles.

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12
Q

Causes of ture hyperkalemia

A

Hypoaldosteronism
Renal tubular acidosis
Renal failure

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13
Q

CEA

A

Nonspecific family of surface glycoproteins expressed in many cancers (GI). Can be used for monitoring, not screening or diagnosis.

May transiently increase during chemotherapy. Higher in smokers.

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14
Q

AFP

A

First expressed in yolk sac, then fetal liver (12wk).

Expressed in many tumors, but L3 variant is somewhat specific for HCC.

Can also be elevated in regenerative states, but very high levels suggest tumor.

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15
Q

PSA

A

Prostatic specific antigen. Binds alpha-2-macroglobulin and alpha-1-antichymotrypsin

Levels of 4-10 are gray; look at free or pro-PSA levels (low % suggest cancer)

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16
Q

CA15-3
CA19-9
CA125

A

CA15-3: Breast (MUC1, also CA27.29)
CA19-9: Lewis A, pancreatic cancer. Can be elevated in cholestasis.
CA125: Ovarian epithelial tumors (except mucinous)

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17
Q

Whipple triad

A

Glucose <45mg/dL, symptoms of hypoglycemia, reversal with glucose administration

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18
Q

DM diagnostic criteria

A
  1. Symptoms

2. Either fasting glucose > 126, random >200, 75g OGTT >200, or A1C > 6.5%,

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19
Q

Detection of diabetes in hemoglobinopathies

A

Cannot rely on A1C due to shortened RBC lifespan. Look at FRUCTOSAMINE

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20
Q

Microalbuminuria

A

Predicts diabetic nephropathy. Precedes decline in GFR.

Start checking annually after T2DM diagnosis, or +5yrs for T1DM.

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21
Q

Creatinine clearance

A

Urine volume * urine creatinine [] / plasma creatinine

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22
Q

MDRD formula

A

Calculates eGFR from Creatinine while considering age, gender, and ethnicity

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23
Q

T3RU test

A

Measures TBG by incubating patient serum and radiolabeled T3 with a resin.

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24
Q

Circulating thyroglobulin

A

Can be used as a marker of residual disease in thyroid cancer (PTC, FTC)

So too can anti-thyroglobulin antibodies, which are sometimes seen.

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25
Q

What causes increases or decreases in TBG?

A

Increases: Estrogen (pregnancy)
Decreases: Cirrhosis, nephrotic syndrome…

Note that TBG does not strongly affect free T3/T4 levels.

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26
Q

Thyroid hormone potencies

A

T3 > T4 > rT3 (inactivated)

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27
Q

Diurnal pituitary hormones

A

CRH/ACTH highest upon waking

GH/GHRH highest upon sleeping

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28
Q

Diagnosis of hypercortisolism

A

Screen with urine free cortisol (24hr) or 1mg overnight suppression

Confirm with LOW-DOSE dexamethasone suppression test

Identify secondary hypercortisolism with ACTH level, HIGH-DOSE dexamethasone suppression

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29
Q

Diagnosis of adrenal insufficiency

A

Urine free cortisol

Cosyntropin test

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30
Q

Metyrapone

A

Blocker of 11-hydroxylase, prevents cortisol production

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31
Q

Aldosterone testing

A

Aldosterone:renin ratio >10 suggests hyperaldosteronism

Lateralize with petrosal sinus sampling

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32
Q

Plasma and urine catecholamine metabolites…

A

Pheochromocytoma: Check urinary fractionated catecholamines or plasma metanephrines
Neuroblastoma: Check urine HMA/VMA levels

Note: 5-HIAA is derived from serotonin, levels elevated in carcinoid syndrome

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33
Q

Prolactin signaling

A

Inhibited by dopamine from hypothalamus. May be the only normal hormone in panhypopituitarism.

Can be promoted by HYPOTHYROIDISM.

High-molecular weight forms may be specific for prolactinoma.

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34
Q

Bilirubin lab analysis

A

Direct bilirubin: Diazo method, does not use any accelerants (only detects conjugated)
Total bilirubin: Diazo method, uses caffeine or methanol to detect all.

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35
Q

Gilbert’s disease

A

UGT1A1 mutation resulting in mildly reduced bilirubin conjugation. Flares with illness, benign.

Reduced metabolism of IRINOTECAN

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36
Q

Dubin-Johnson

A

Mutation of organic anion transporter. Results in direct hyperbilirubinemia and pigmentation of organs

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37
Q

Liver enzymes

A

AST: Nonspecific, also see in skeletal and cardiac muscle (elevated in exercise)
ALT: More specific for liver
GGT: Cholestatic marker, fairly specific
LDH: Non-specific, fast clearing

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38
Q

Liver autoantibodies

A 
AMA - PBC, especially PDC-M3 variant
ASMA - Type 1 AIH
Anti-LKM - Type 2 AIH
Anti-soluble liver antigen - Type 3 AIH
pANCA - PSC
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39
Q

Wilson’s disease

A

ATP7B transporter defect with resultant tissue accumulation of copper.

When not active/fulminant, low ceruloplasmin & copper. Otherwise note hemolysis

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40
Q

Hereditary hemochromatosis

A

XXXXXX

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41
Q

DeRitis Ratio

A

AST:ALT

Normally ALT > AST, but in alcohol, Wilson, cirrhosis, the ratio is reversed

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42
Q

Lactate dehydrogenase fractions

A

Normally LD2 > LD1 (both very common).

LD1 elevation / flipped ratio can be seen in acute infarctions or hemolysis.

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43
Q

Alkaline phosphatase

A

Many isoenzymes, can be distinguished by electrophoresis or heat inactivation

“Bone burns, liver lingers”.

Regan isozyme - Placenta, tumors

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44
Q

Biliprotein

A

Bilirubin + albumin; accumulates in cholestatic states and takes days to clear.

45
Q

Amylase

A

Elevated in pancreatitis, sialadenitis (lipase normal), macroamylasemia (spurious complex)

Less specific than lipase.

Needs calcium as a chelator, do not draw in blue/lavender tops.

46
Q

D-xylose test

A

Measures gut absorptive capacity (not pancreatic exocrine function)

47
Q

Fecal elastase

A

Superior to fat analysis or fecal chymotrypsin to assess pancreatic exocrine function

Must be performed on well-formed stools.

48
Q

Troponins

A

Complex consists of cardiac troponins C (calcium), I, T (tropomyosin).

C: Same in cardiac and skeletal
I: Specific.
T: Specific.

49
Q

CK-MB, myoglobin

A

CK-MB: Outdated MI marker.

Myoglobin: Totally nonspecific, but fast to rise and fast to fall.

50
Q

NT-proBNP

A

Superior to biologically active BNP or ANP. Reflects systolic (not diastolic dysfunction)

51
Q

MI diagnosis

A

Troponin >99th percentile

One of: Symptoms, EKG abnormality, or wall motion abnormality

52
Q

ACE

A

Can be elevated in sarcoidosis

53
Q 
Macro CK
Mitochondrial CK (macro CK type 2)
A

Macro CK: Immunoglobulin complex seen in some elderly women

Mitochondrial CK: SUggestive of some advanced malignancies.

54
Q

hsCRP

A

Predictor for development of acute coronary syndrome

JUPITER study

55
Q

Cryoglobulinemias

A

Type I: Monoclonal only; associated with lymphoproliferative disorders
Type II: Monoclonal and polyclonal component; associated with HCV
Type III: Polyclonal only; associated with autoimmune disorders

56
Q

Calcium assay

A

Colorimetric assay

Ionized assay

57
Q

Urinary CAMP

A

Increased in hyperparathyroidism

58
Q

Forms of parathyroid hormone

A

Intact - Active, short-lived
N-terminal - Active, short-lived
C-terminal - Inactive, long-lived

59
Q

Co-oximetry

A

Uses 4 wavelengths of light

Distinguishes oxyhemoglobin, deoxyhemoglobin, carboxyhemoglobin, methemoglobin

Does not detect sulfhemoglobin

60
Q

FSH/LH secretion

A

Responds to continuous GNRH secretion (continuous inhibits)

Surge in ovulation. Estrogen predominates in follicular phase, progesterone in luteal phase.

61
Q

Estrogens

A

E1: Estrone, mostly post-menopausal
E2: Estradiol, most potent
E3: Estriol, placental/pregnancy

62
Q

AMH

A

Produced by granulosa cells, marker of ovarian reserve. Elevated in PCOS due to failure of selection of a dominant follicle.

63
Q

hCG in pregnancy

A

Doubles every two days (if normal intrauterine)

Peaks at end of third trimester, holds through pregnancy

Takes 2 weeks postpartum to clear

*Hyperglycosylated form predominates in early pregnancy

64
Q

First trimester screen

A

hCG, PAPP-A, nuchal thickness.

For down syndrome.

65
Q

Quad screen

A

hCG / Inhibin / Estriol / AFP

t21: + / + / - / -
t18: - / - / - / -
NT defect: AFP elevated

66
Q

MSAFP

A

If >2.5 MoM, high risk of birth defects.

LOW in t21!

67
Q

Markers of fetal lung maturity

A

LS ratio of 2.5:1 (less lecithin suggests immaturity)
PG concentration
Lamellar body count (more = mature)

68
Q

Pregnancy marker changes

A

eGFR increases&raquo_space; lower creatinine, BUN. Proteinuria, glucosuria

Increased fibrinogen, (relatively) decreased albumin

Dilutional anemia despite increase in red cell mass

69
Q

Lipoprotein compositions

A

Chylomicrons: Triglycerides.
VLDL: Triglycerides.
LDL: Cholesterol, Apo-B100
HDL: Cholesterol, Apo-A

70
Q

Friedewald calculations

A

VLDL is estimated as TG/5.

LDLc = TC - HDL - VLDL

71
Q

Abetalipoproteinemia

A

Low triglycerides and low cholesterol.

ACANTHOCYTES on peripheral smear.

Developmental delay, fat malabsorption…

72
Q

Frederickson phenotypes of hyperlipidemias

A

I - Hyperchylomicronemia (TGs, LPL or ApoC2 def)
II - A (LDL), B (VLDL, LDL)
III - ApoE2/E2
IV - VLDL, associated with insulin receptor mutations and lipodystrophy
V - Chylomicrons, VLDL

73
Q

LPL effect
LCAT effect
CETP effect

A

LPL: Hydrolyzes VLDL to form IDL/LDL
LCAT: Transfers lipids to HDL
CETP: Exchanges lipids between HDL and lower density particles

74
Q

Tangier disease

A

Autosomal recessive disorder of absent HDL.

75
Q

ATP III recommended targets

A

TC: <200
LDL: Optimal <100, near optimal 100-129, borderline 130-159
HDL: <40 low, >60 high

76
Q

GDM testing

A

2-step: 50g OGTT (target X), then 100g OGTT (target Y

1-step: 75g OGTT (target 180, 153 at 1, 2 hours)

77
Q

Fecal occult blood testing

A

Guaiac based testing prone to false-positives (NSAIDs, red meat, peroxidase (horseradish)) and false-negatives (Vitamin C consumption)

Immunochemical based methods are less affected.

78
Q

Euthyroid sick syndrome

A

Low T3, T4
Elevated rT3?
Nomral TSH.

Just peripheral inactivation of thyroid hormone. Thyroid function is normal.

79
Q

T3RU

A

Measures available binding sites on thyroid binding globulins.

Mix patient sample with radioactive iodine (binds available sites), then resin-adsorb and see how much radioactive iodine remains.

High residual levels means few binding sites (hyperthyroidism). Low residual levels in hypothyroidism.

80
Q

High-dose dexamethasone suppression

A

Distinguishes pituitary corticotroph adenoma (Cushing disease) which should suppress from ectopic ACTH production (does not suppress).

81
Q

Granulosa cells - Hormonal profile

A

Secretes both steroid hormones (testosterone, estrogen, etc) and peptide hormones (AMH, inhibin).

May have elevated AFP serum levels (not CA-125!)

82
Q

Confirmatory test for Conn syndrome

A

Isotonic large volume saline infusion&raquo_space; failure to suppress aldosterone

83
Q

Gestational thyrotoxicosis

A

Elevated bHCG levels cross-react on TSH receptor. Should co-occur with hyperemesis gravidarum

84
Q

CTX, NTX

A

Bone resorption markers.

High variability according to diet, circadian rhythm

85
Q

Pseudohypoparathyroidism

A

Peripheral resistance to PTH.

Associated with GNAS (McCune-Albright)

86
Q

Apt test

A

Distinguishes fetal hemoglobin from adult; fetal hemolysate resists denaturing in 1% NaOH

87
Q

IBD serologies

A

Crohn’s: Anti-saccharomyces cerevisiae (ASCA)

UC: pANCA (as in PSC)

88
Q

Schilling test

A

Test for failure of B12 absorption. Give oral load of radiolabeled B12, inject non-radiolabeled. Measure urine.

Done in stages with progressive replacement of IF, pancreatic enzymes

89
Q

Celiac serology

A

TTG is best test for diagnosis

Anti-endomysial IgA (EMA) may disappear after diet improvements

90
Q

Carbohydrate-deficient transferrin

A

Old, shitty test for alcohol abuse

91
Q

Non-HBV hepatitis serologies

A

Anti-HAV: Total for screen, IgM for confirm

Anti-HCV: IgG only (no IgM)

92
Q

Hyperviscosity

A

Falsely depresses most assays/analytes

93
Q

Timing of cardiac biomarkers

A

Myoglobin rises and falls first

CK-MB and troponins all have similar timing (detectable in 4-6 hrs, peak in 10-24hrs)

94
Q

Skin sweat chloride test

A

Gold standard for CF diagnosis.

Performed using coulometric titration

95
Q

Grey-tops

A

Contains sodium fluoride to halt in-tube glycolysis. For glucose measurements.

96
Q

Jaffe reaction

A

Detects creatinine by forming a chromogen (alkaline picrate). Affected by interfering substances ~520nm.

97
Q

Convert urea to BUN

A

Divide by molar ratio of nitrogen to urea molar weight– 60/28, or divide by 2.14.

98
Q

Pseudohypokalemia

A

Can be seen in some leukemic specimens; cells (especially blasts) may take up extracellular potassium

99
Q

Fatty- acid oxidation defects

A

Usually present with hypoglycemia and low ketones (cannot mobilize fat stores)

100
Q

Most common urea cycle defects

Most common organic acidemias

A

Urea cycle: Ornithine transcarbamylase deficiency (X-linked recessive)
Organic acidemias: Methylmalonic, priopionic acidemias

101
Q

Transient hyperkalemias

A

Exercise

Shift to upright positioning (third-spacing of free water)

102
Q

Familial hyperkalemia

Familial hypocalciuric hypocalcemia

A

FH: Autosomal dominant defect of RBC membrane&raquo_space; leakage in storage
FHH: Benign condition of decreased urine calcium excretion&raquo_space; as name suggests

103
Q

RTAs

A

Type 1: Distal. Poor hydrogen excretion means urine cannot acidify. Alkaline urine. Hyperchloremic.
Type 2: Proximal. Failure to reabsorb bicarb, but distal compensation can acidify urine. Hyperchloremic.

Type 4: Failure of aldosterone. Hyperkalemic! Acidic urine.

104
Q

Pseudohypoparathyroidism

A

Renal disease

Low calcium, high potassium

High parathyroid hormone

105
Q

NAD+, NADH absorption

A

NAD: 260nm
NADH: 340nm

Can see interference with lactic samples or high LDH samples

106
Q

Rickets

A

Low calcium, LOW PHOSPHATE, high PTH

107
Q

Procalcitonin

A

Inflammatory marker that is suggestive of bacterial infection

108
Q

Testosterone testing

A

Immunoassays (insensitive, only use in men or when high levels are expected)

Mass spec (for women, children, tumors?)

109
Q

Triglyceride testing

A

Relies on hydrolysis of glycerol; false elevations may be seen in hyperglycerolemic states (glycerol kinase deficinecy)

Tim's CP Board Review (16 decks)

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