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PA MS > Lab medicine > Flashcards

Lab medicine Flashcards

1
Q

What is the definition of sensitivity ?

A

Sensitivity is defined as the proportion of the people with the target disease who test positive.

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2
Q

A sensitive test is used to ?

A

exclude or rule out the disease

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3
Q

How to mathematically calculate sensitivity ?

A

TP/ TP+ FN

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4
Q

Specificity is defined as ?

A

Specificity is the proportion of people WITHOUT the target Disease that have a NEGATIVE blood test.

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5
Q

A specific test is used to ?

A

A specific test is used for ruling in a disease, as it rarely misclassifies those WITHOUT a disease as being sick

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6
Q

How to mathematically calculate specificity ?

A

TN/ TN+ FP

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7
Q

definition of positive predictive value

A

Positive Predictive Value (PPV) is the proportion of those with a POSITIVE test that have the target disease in a population.

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8
Q

Mathematical estimation of positive predictive value ?

A

TP / TP+FP

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9
Q

Definition of negative predictive value ?

A

Negative Predictive Value (NPV) is the proportion of those with a NEGATIVE blood test that do not have the target disease in a population.

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10
Q

Mathematical estimation of negative predictive value ?

A

TN/TN+FN

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11
Q

What is the limitation of predictive values?

A

The positive and negative predictive values are specific to the population in questions. Therefore, comparison of predictive values with an incongruent population will be meaningless.

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12
Q

What are the types of Urine Studies

A
  • Rapid urine test (dipstick)
  • Urinalysis
  • Urine culture
  • 24-Hr urine collection
  • Urine drug screen / urine toxicology screen
  • Pregnancy test
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13
Q

What are the components of Urine dipstick ?

A
  1. pH – dehydration, diabetes, infection, acid/base d/o, kidney disease
  2. Specific gravity - dehydration
  3. Glucose - diabetes
  4. Ketone - diabetes
  5. Nitrite - infection
  6. Leukocytes - infection
  7. Protein – kidney disease, diabetes, HTN
  8. Blood – kidney disease, infection, stones, prostate dz, bladder dz/CA
  9. Bilirubin – liver disease, gall bladder disease
  10. Urobilinogen – liver disease, haemolytic anaemia
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14
Q

What are the steps of urinalysis ?

A
  • Gross inspection
  • test strip
  • Microscopy
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15
Q

Gross inspection looks for

A
  • Color
    *Turbidity
  • Odour
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16
Q

Purpose of urinalysis ?

A

To look for microbes, urine casts in the context of kidney disease and infections, to look for crystals and creatinine.

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17
Q

What is the definition of urine specific gravity ?

A

USG is defined as the ratio between the density of urine and the density of an equal volume of pure distilled water.

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18
Q

Normal urine specific gravity ?

A

1.016 to 1.022

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19
Q

Normal urine volume ?

A

1000 to 1600 ML/Day

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20
Q

Oliguria

A

< 500 cc/day

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21
Q

Anuria

A

<100 cc /day

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22
Q

Polyuria

A

> 2500 to 3000 cc/day

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23
Q

Normal urine PH

A

4.5 to 6.5

24
Q

Normal Glomerular capillaries are permeable to molecules of what size ?

A

<20,000 dalton.

25
Q

what is the purpose of 24 Hr urine collection ?

A

It is used detect adrenal diseases by detecting adrenal hormones in urine/ kidney diseases, parathyroid gland diseases.

26
Q

urine drug screen is a qualitative study: commonly screened drugs are ?

A
  • Amphetamines (1-4d)
  • Barbiturates (2-4d)
  • Benzodiazepines (1-30d)
  • Cannabinoids (1-30d)
  • Cocaine (2-7d)
  • Opiates (1-6d)
  • Phencyclidine (4-30d)
27
Q

Urine pregnancy test ?

A

test for Beta human chorionic gonadotropin levels produced by the placenta.

28
Q

What are Cardiac Troponin T (cTnT) and HS-Cardiac Troponin T (cTnT)?

A

They are highly sensitivity markers of acute cardiac injury and they peak very early in the blood than most other markers.

29
Q

Explain why brain natriuretic peptide (BNP) will be elevated in periods of exacerbation of underlying heart failure ?

A

BNP and NT-proBNP are reflexively released by the ventricular cardio-myocytes in response to volume and pressure overload as seen in CHF.

30
Q

How BNP and NT-proBNP can be used to evaluate heart failure?

A

an increase BNP >100 pg/L is indicative of CHF.
NT-proBNP level > 450 pg/L in people <50, >900 pg/L between 50-75 years, and > 1800 pg/L in people >75 is suggestive of CHF.

31
Q

What are the components of liver profile ?

A

*alanine aminotransferase (ALT), *aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), *5’nucleotidase,
*total bilirubin: conjugated (direct) bilirubin, unconjugated (indirect)bilirubin
*prothrombin time (PT)
*the international normalized ratio (INR)
*lactate dehydrogenase
*total protein
*globulins
*albumin.
* G/A ratio

32
Q

Albumin/Globulin ratio higher or lower than normal are associated with ?

A

liver and/or kidney disease

33
Q

hepatocellular pattern ?

A

Elevated aminotransferases out of proportion to alkaline phosphatase

34
Q

Cholestatic pattern?

A

Elevated alkaline phosphatase +gamma glutamyl transferase + bilirubin out of proportion to AST and ALT

35
Q

AST vs ALT

A

AST is an amintransferase that is neither specific nor sensitive to liver disease as it is a cytosolic and mitochondrial isoenzyme found in many organs other than the liver. Whereas ALT is highly specific and sensitive to the hepatocellular injury.

36
Q

Albumin in liver disease ?

A

relatively unaffected in acute injury and reduced in chronic liver disease.

37
Q

Alkaline phosphate in biliary disease ?

A

ALP is a zinc metalloenzyme highly concentrated in the in the microvilli of the bile canaliculus. It is a marker of Biliary tree or duct obstruction.

38
Q

Gama Glutamyltransferese significance ?

A

the elevation of the glycoprotein GGT is seen in hepatobiliary disease. Highly sensitive for high alcohol consumption and drug addiction.

39
Q

clinical significance of testing pancreatic enzymes.

A

They are elevated in pancreatic injuries. Lipase is a more useful marker of acute pancreatitis as it has longer duration of elevation than amylase.

40
Q

ESR

A

it is the rate at which blood cells settle in a test tube. It is a marker of chronic and acute inflammation.

41
Q

C-reactive protein

A

CRP is elevated in acute and chronic inflammation. It is produced by the liver in response to acute inflammation.

42
Q

Triglyceride, HDL, and Total cholesterol are ?

A

directly measured.

43
Q

LDL is estimated using the formula

A

Total cholesterol - HDL- ( Triglyceride/5)

44
Q

Non-HDL cholesterol is estimated by

A

Total cholesterol- HDL

45
Q

Indication for blood culture ?

A

To detect bacteraemia ( transient, intermittent, continuous or sepsis and shock).

46
Q

collection procedure of blood sample for culture in sepsis ?

A
  • 3 samples at an interval of 30 to 60 min.
  • ideally one sample before fever spike.
  • Must be done before antibiotics started
  • positive samples should be subcultured on Agar plates.
47
Q

If two or more samples positive and
clinical presentation consistent with
infection ?

A

Treat identified organism based
on susceptibility

48
Q

If one sample positive in blood culture ?

A

**Treat if organism is HIGH probability of true
positive AND clinical indications still present
*Don’t treat if organism is LOW probability
**If INTERMEDIATE probability, clinical
judgement and/or retesting

49
Q

Nucleic Acid Amplification ?

A

is a highly sensitive laboratory technique to detect causative organism such as respiratory panel , HIV load , HCV, HSV etc.

50
Q

Use of serology ?

A

Serology is used to detect host antibodies against the antigens of known pathogens.

51
Q

Antigen detection

A

It is used to detect specific antigens + ca not distingusih viable from non viable.

52
Q

Indication for prothrombin time ?

A

*Assess for suspected abnormalities of the extrinsic and final common pathway
*Monitor warfarin therapy
*Assess synthetic function of the liver (eg, in liver failure)
*Evaluation of unexplained bleeding
*Diagnose DIC

53
Q

aPTT

A

*Assess for suspected abnormalities of the intrinsic and final common pathway
*Monitor heparin therapy (in patients on unfractionated heparin infusions)
*Assess synthetic function of the liver (eg, in liver failure)
*Evaluation of unexplained bleeding
*Diagnose DIC

54
Q

How is INR calculated

A

Patients PT/ Control PT
Normal INR = 1

55
Q

Normal INR on warfarin therapy

A

2.5 ( 2.0-3.0)

56
Q

Normal eGFR

A

> 90

PA MS (44 decks)

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