24 - Fundamentals of Clinical Lab Flashcards

(41 cards)

1
Q

Difference between

Invasive vs Non-invasive

Tests

A

Invasive tests** use a **DEVICE
needle / tubes -> to enter body to collect samples

Noninvasive tests use samples obtained WITHOUT DEVICE
exhaled air / sputum/ urine

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2
Q

Difference between

Analyte vs Biomarker

A

Analyte = substance measured by an assay/test
ex. proteins / drugs / vitamins / hormones
typically contained in a specimen / sample

Biomarker** = **characteristic that is objectively measured/evaluated
as an INDICATOR OF A BIOLOGICAL PROCESS
drug response / pathology

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3
Q

Aside from Blood / Urine what are some

Less-Common Samples?

A
  • *Feces**
  • *Occult Blood** test

Sweat
analysis of increased electrolytes for CYSTIC FIBROSIS

Saliva
analysis of drugs / virus / bacteria

Synovial / Cerebrospinal / Amnionic

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4
Q

Common ANALYTES examined in physiological samples

A

Proteins / AA’s / Nitrogen metabolites

Electrolytes / trace elements

Lipids / Enzymes / Hormones

Drugs / Vitamins / small organics

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5
Q

What are some of the Most Common Errors

in Sample Analysis

and how can we avoid them?

A

MIS-IDENTIFICATION of the patient
check/confirm patients name & ID etc

Add more information

  • *MIS-LABELED samples**
  • usually only found when test results are UNEXPECTED*
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6
Q

Pharmacist role in Clinical Labs

A

Interpreting Lab Results
basic grasp of lab terminology / technology / statistics of testing

Pharmacists may be involved in:

Sample Collection / Handling

Reporting / Disposal

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7
Q

PRE-Collection Causes of VARIABILITY

in sample colection

A

Circadian Rhythms
the 24 hour cycle of concentration of various biochemicals in the body:
Melatonin = excreted in darkness
Iron / Acid Phosphatase / Electrolytes / Bone-turnover markers

  • *Diurnal Changes**
  • *TIMING** - Sleep / Wake cycle needs to be considered
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8
Q

Affect of Supine -> Standing on sample collection

Physiological Variable - Posture

A
  • *Supine -> Standing**
  • Reduce pt’s blood volume by 10%,*

which in turn INCREASES:
apparent concentration of drugs / enzymes / calcium

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9
Q

Affect of UPRIGHT POSTURE on sample collection

Physiological Variable

A

Upright:

Induces LOW SECRETION of Various Hormones:

Catecholamines / Aldosterone / Renin / Others

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10
Q

Affect of Prolonged Bed Rest on sample collection

Physiological Variable

A

Fluid RETENTION

Lower concentrations of PROTEINS

induces elevated NITROGEN EXCRETION

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11
Q

Affect of Brief / Mild Exercise on sample collection

Physiological Variable

A

strenuous exercise -> exaggerated effects of mild exercise

RAISE:

Blood Glucose / Lactate / Several Enzymes

Decrease:

serum TG’s / Cholesterol
can persist for days

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12
Q

Affect of FOOD INGESTION on serum collection

Physiological Variables

A

RAISES levels of many analytes:

Glucose / TG’s

Iron / Sodium / Lactate Dehydrogenase

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13
Q

Blood Collection Technique

Blood has: Plasma / RBC / WBC / Platelets

serum = liquid that seperates when blood clots

A

Venipuncture = Phlebotomy, injection into the blood vessel

done AFTER 20 MIN REST, avoid HEMODILATION effects

Clean/Dry site, no alcohol remaining

collected in:

  • *VACUTAINERS** = Evacuated tubes, closed by rubber septum
  • different interior coats to promote/retard clotting*
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14
Q

Difference between

HEPARIN Plasma & SERUM

A

Heperinized plasma = Serum with fibrinogen (it clotted)

Serum then has lower TOTAL protein

Serum is HIGHER in potassium from platelets
platelets –> release potassium during clotting

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15
Q

Heparin Related ERRORS

A

heparin can displace Thyroxine from serum proteins

  • -> Falsely HIGH reading
  • *thyroid issue**

Heparin salts contain ammonium or lithium
–> falsely HIGH readings of these cations

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16
Q

EDTA related ERRORS

EDTA chelates divalent metal ions = Ca / Fe
inactivates certain enzyes

A
  • *Collect EDTA-blocked samples LAST!!!**
  • to avoid cross-contamination*

EDTA will PROLONG CLOTTING TIMES
due to calcium chelation

  • may lower / falsely low readings of:*
  • *iron / calcium / magnesium**
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17
Q

Blood sample POST-Collection Errors

A

Delays of <1 hour are generally well tolerated

Avoid THAWING of frozen samples

For Remote sites: best to
Seperate Plasma/serum physically from cells BEFORE transport

18
Q

Vacutainer

A

Evacuated tubes, closed by a rubber septum
used for BLOOD SAMPLES

Different sizes / interior coatings that
PROMOTE/RETARD CLOTTING

often have a preferred order in which they are drawed

19
Q

What are the 3 Types of URINE SAMPLES?

A

Random Sample
Timing is not critical, used typically for drugs of abuse

FIRST MORNING = 8-hour sample
most Concentrated, preferred for microscopic exam
testing for proteins / homones, that may have intrinsicly low conc.

Timed Specimen
patient may need cautions on diet restrictions / drug ingestion
1 / 4 / 24 hour etc

20
Q

What is a Clean-Catch Specimen?

Urine Samples

A
  • *MID-STREAM** Sample
  • however first 10mL is useful for bacterial examination*

no contact w/ bacteria or foreign substation
or perineum

Sterile Container

Double-Voided Sample
timed sample following complete bladder emptying:
done esp for glucost tolerance test (GTT)

21
Q

Accuracy is a measure of ?

A

NON-Random / Systematic Error or Bias

How FAR your measurement is
from the TRUE value

22
Q

Precision is the descriptor of?

A

RANDOM VARIATION in a population of data

Ability to produce the same value in REPLICATE testing

23
Q

Diagnostic SENSITIVITY

and its Math value

A

“senSITIVE = poSITIVE”

The probability that a lab test is POSITIVE,
in the presence of disease

  • can use more dilute samples,
    mathmatically: *

True Positives
( True Positives + False Negatives )

24
Q

Diagnostic SPECIFICITY

A

The probability that a test will be NEGATIVE,
in the absence of disease

mathmatically:

True Negatives
( True Negatives + False Positives )

25
**Where do we want the curve to be?**
to go **_UP_** Increase True Positive Fraction , SenSITIVITY To the **_RIGHT_** *Decrease False Positive Fraction = Specificity* Increase True Negative Fraction = lower x axis Specificity
26
**SenSITIVITY vs Specificity PLOT**
Use the **calculations for BOTH Sensitivity & Specificity to PLOT** **Y =** **True Positive Fraction (SenSITIVITY)** * *Top X** = ***False Positive*** Fraction ( **Specificity )** * Bottom X =* True Negative Fraction ( Specificity ) Want the curve to go **_TOP RIGHT_**
27
**True *Negatives* \>\>\>\>\> *False* Positives** What type of **Diagnostic Test** do we have?
**_GOOD Specificity_** *_True Negatives_* ( True *Negatives* + *False* Positives )
28
**True** **Positives** \>\>\>\>\> ***False Negatives*** What type of **Diagnostic Test** do we have?
**_Good SenSITIVITY_** **_True Positives_** ( **True Positives + *False negatives*** )
29
**What would we like to see in** **Test Result Distribution**
**_GOOD SEPERATION_** But we typically see **overlap** ~ **5%**
30
**Reference VALUES** are determined as......?
RV are deterimined as **_AVERAGES**_ or _**a RANGE of values_** drawn from a **population of *usually* healthy adults**
31
**_Reference RANGES_** can be defined for ......?
RR can be definied for **_any CHOSEN population_** like **adults vs children Males vs females** Normal range includes **95% of the population** *5% will have abnormal test results*
32
What are **Qualifications** in Populated distributions? ## Footnote *distributions may NOT be bell-shaped*
**Sex / Age** Genetics / FMH Physiology / Environment / Socioeconomic status
33
**_Computer-Based AIDS for Error Detection_**
Comparison of **_present samples w/ previous samples_**​ **_DELTA CHECK_** tests for results that vary by a **pre-set amount or %**
34
Whats is a **DELTA CHECK?**
Tests for results that **VARY** by a **_pre-set amount or %_** that is determined by **Referencing steps** Most useful for analytes that **_do NOT vary from DAY to DAY_** *do not use for analytes that are HIGHLY VARIABLE = glucose*
35
**Reference Terminology/Steps**
Used to detemine the **pre-set amount or % in a DELTA CHECK** **Individuals** make up a **Population** from which is selected a **Sample Group** on which are determined **Values** over which is observed a **Distribution** (**obvserved value**, individual may be compared here) from which are calculated **Limits** that may define **Intervals** **I P S V D L I**
36
**Analytes that are _APPROPRIATE_ for Delta Check Analysis**
***_Little day to day variation_*** **ELECTROLYTES** = Na / K / Cl **Total Protein / Albumin** Urea / Creatinine **_Alkaline Phosphatase_** (only enzyme) **hemoglobin / hematocrit**
37
**Analytes that are *_INAPPROPRIATE_* in Delta check Analysis**
may **VARY CONSIDERABLY** by individuals **GLUCOSE** **Phosphate** **Enzymes,** *except alkaline phosphatase* LDH / Creatine Kinase **AST / ALT**
38
**Common causes of FAILED Delta Checks**
Specimin **drawn from ABOVE an** **IV Line** --\> ***_dilution_***, solution upstreme is diluted **Contamination** specimen **Mis-Identified** specimen
39
**Tests that are subject to CYCLICAL VARIATION**
**ELECTROLYTES** = Na / K / Phosphate **Renin / Aldosterone** **TSH / PTH Glucose** **Iron / Osteocalcin** **Catecholamines** Acid Phosphatase / ACTH / Collagen / Cortison Gastrin / GH / Prolactin
40
**Tests that are Affected by EXERSISE**
**_MUSCLE ENZYMES = CK / ASK / ALT / LDH_** **Potassium / Phosphate URIC ACID BILIRUBIN** Glucose / Gonadotropin / Sex steroids **Cholesterol / TG's**
41
**Tests Affected by RECENT Meals**
* **_Sodium / Cholesterol_*** * not immediately after a single meal, just over a SEVERAL DAYS* **Gastrin / Glucagon / Insulin** **TG's / urine pH** **Cl / Ca / K / P**