Quality Control (Clinical Chemistry)

Question 1

3 parts of Pre-analytical phase

Answer 1

• Patient Identification
• Patient Preparation
• Phlebotomy

Question 2

The process of verifying a patient’s identity, is the most important step in specimen collection.

Answer 2

Patient identification

Question 3

Why patient identification is the most crucial part of pre analytical phase?

Answer 3

Patient identification is defined as the process of verifying a patient’s identity and is also considered as the most crucial step of specimen collection. It is necessary in the laboratory testing process due to the fact that misidentifying a patient specimen or collecting specimen from the wrong patient can lead to fatal and detrimental repercussions.
Furthermore, if proper patient identification is not followed religiously the results that the laboratory will release cannot be reliable for the proper diagnosis of the patient and this can result and misdiagnosis of disease and the conduct of improper treatment leading to substandard and poor patient outcomes

Question 4

Guidelines that (Accuracy in Patient and
Sample Identification) recommends having the patient spell the last name.

Answer 4

CLSI guideline GP33-A

Question 5

What is the minimum identifier?

Answer 5

• 2
• name and birthdate

Question 6

Hormone that is being collected while the patient is sleeping

Answer 6

Cortisol

Question 7

3-Way IDENTIFICATION

Answer 7

1) patient’s verbal ID statement,
2) check of the ID band,
3) visual comparison of the labeled
specimen with the patient’s ID band
before leaving the bedside.

Question 8

it is a part of the process management component of the quality system that integrates good laboratory practices to ensure correct patient results

Answer 8

Quality control

Question 9

it is the process of ensuring that analytical results are correct by testing known samples that resemble patient’s sample and comparing their determined values with their expected values
(control values)

Answer 9

Quality Control

Question 9

it is the process of ensuring that analytical results are correct by testing known samples that resemble patient’s sample and comparing their determined values with their expected values
(control values)

Answer 9

Quality Control

Question 10

What are objectives of Quality control?

Answer 10

• To check the stability of the machine
• To check the quality of reagents
• To check technical errors (personnel)

Question 11

process of verification by comparing the accuracy of the measuring instrument against a reference standard

Answer 11

Calibration

Question 12

• This are substances with known concentration used
• It is done every 6 months or more frequently if recommended
by the manufacturers

Answer 12

Reference Standard

Question 13

2 types of reference standard

Answer 13

o Primary Standard
o Secondary Standard

Question 14

Is an ultra-high purity grade compound used in analysis involving assay, identification or purity tests
- Reference material

Answer 14

Primary standard

Question 15

These are also high purity grade materials which are quantified in relation to primary standards and put to routine use in laboratories.
- most commonly used in the lab

Answer 15

Secondary standards

Question 16

Characteristic of an ideal QC materials

Answer 16

• It should resemble human sample
• Inexpensive and stable for long periods
• No communicable diseases
• No matrix effects/known matrix effects
• With known analyte concentrations
• Convenient packaging for easy dispensing and storage

Question 17

2 Types of quality control

Answer 17

• INTERNAL QUALITY CONTROL (Intralaboratory Quality control)
• EXTERNAL QUALITY CONTROL (Interlaboratory Quality control)

Question 18

• Analyses of control samples together with the patient specimens
• Daily monitoring of accuracy & precision of analytical methods.
• Detection : Random and Systematic error

Answer 18

INTERNAL QUALITY CONTROL (Intralaboratory Quality control)

Question 19

• It involves the proficiency testing programs that periodically provide samples of unknown concentrations to participate in clinical laboratories
• It is important in maintaining long-term accuracy of the analytical methods

Answer 19

EXTERNAL QUALITY CONTROL (Interlaboratory Quality control)

Question 20

What is the gold standard for clinical laboratory external QC testing?

Answer 20

College of American Pathologists Proficiency program

Question 21

2-level os control solutions

Answer 21

Clinical Chemistry

Question 22

3-Level Control Solutions

Answer 22

Immunology

Question 23

It is the nearness or closeness of the assayed value to the true or target value

Answer 23

Accuracy

Question 24

accuracy is estimated using three different types of studies:

Answer 24

1. Recovery 2. Interference Studies 3. Patient Sample Comparison

Question 25

degree by which a method is easily repeated

Answer 25

Practicability

Question 26

ability of the method to maintain accuracy and precision over a period of time

Answer 26

Reliability

Question 27

(Imprecision; Indeterminate) affect the precision of the test system (e.g., pipetting technique) - Human error - not preventable

Answer 27

Random error

Question 28

(Inaccuracy/ Determinate) affect the accuracy of the test system - Preventable - there is trend

Answer 28

Systematic error

Question 29

a sudden upward or downward change that lasts for four or more consecutive values (e.g., equipment malfunction, instrument adjustments)

Answer 29

Shift

Question 30

tendency of results to gradually increase or decrease over a period of time (e.g., contamination, reagent deterioration gradual equipment failure)

Answer 30

Trend

Question 31

Values: far from the main set of values Highly deviating values Random or systematic errors

Answer 31

Outliers

Question 32

Degree of flatness or sharpness

Answer 32

Kurtosis

Question 33

National reference lab for Clin chem

Answer 33

Lung Center of the Philippines

Question 34

National reference lab for Toxicology

Answer 34

East Avenue Medical Center

Question 35

What is the most common laboratory tests performed in the external quality control or in clinical chemistry?

Answer 35

- FBS (Glucose) - BUN - Uric acid - Creatinine - Cholesterol - Triglyceride - Total protein - Albumin - Sodium

Question 36

used to observe values of control materials overtime to determine and detect errors such as inaccuracy and imprecision.

Answer 36

QC charts

Question 37

• This plot will give the earliest indication of systematic errors (trend) and can be used with 13s rule. • Very sensitive to small, persistent errors that commonly occur in the modern, low-calibration frequency analyzer

Answer 37

Cumulative sum (CUSUM)

Question 38

It is used to compare results obtained on a high and low control serum from different laboratories

Answer 38

Youden/twinplot

Question 39

• Dot chart • Most widely used system in clinical laboratory • Allows the laboratorians to apply multiple rules without the aid of a computer • Easy identification of random and systematic errors.

Answer 39

Shewhart-levey jenings chart

Question 40

• Present in all measurement; due to chance • Basis for varying differences between repeated measurements • Due to instrument, operator & environmental conditions.

Answer 40

Random error

Question 41

• Is an error that influence observations consistently in one direction • Detected either positive or negative bias.

Answer 41

Systemic error

Question 42

What are the random errors?

Answer 42

• Pipetting errors • Mislabeling of samples • Temperature and Voltage fluctuation • Improper mixing of samples & reagent • Dirty optics

Question 43

What are the systematic errors?

Answer 43

• Calibration problem • Deterioration of reagents & control • Unstable and inadequate reagent blanks • Contaminated solutions • Failing instrumentation • Poorly written procedures • Incorrect sample & reagent volume

Question 44

A pair of medical decision points that span the limits of results expected for a defined healthy population

Answer 44

Reference Interval

Question 45

What are the applications of reference intervals that can be grouped into three main categories?

Answer 45

1. diagnosis of a disease or condition 2. monitoring of a physiologic condition 3. monitoring therapeutic drugs

Question 46

Range of values that include a specified probability, usually 90% or 95% - we are using the 95% (±2SD)

Answer 46

Confidence Interval

Question 47

defines the interval by the mean ±1.96 SDs = 𝑥 ±1.96 SD

Answer 47

Parametric Method

Question 48

the reference interval is determined by using the central 95% of values; the reference range is therefore defined by the 2.5th to the 97.5th percentiles - usual/most commonly used

Answer 48

Non-Parametric Method

Question 49

is the ability of the analytical method to measure the smallest concentration of the analyte of interest • screening test

Answer 49

Analytical Sensitivity

Question 50

is the ability of an analytical method to measure only the analyte of interest - Confirmatory test

Answer 50

Analytical Specificity

Question 51

- ability of a test to detect a given disease or condition - proportion of individuals with that disease who test positively with the test

Answer 51

Diagnostic Sensitivity

Question 52

- ability of a test to correctly identify the absence of a given disease or condition - proportion of individuals without a condition who have a negative test for that condition

Answer 52

Diagnostic Specificity

Question 53

the predictive value of a positive test refers to the probability of an individual having the disease if the result is abnormal ("positive" for the condition)

Answer 53

Positive Predictive Value

Question 54

refers to the probability that a patient does not have a disease if a result is within the reference range (test is negative for the disease)

Answer 54

Negative Predictive Value

Question 55

±1𝑆𝐷 =

Answer 55

68.3% 𝑜𝑓 𝑜𝑏𝑠𝑒𝑟𝑣𝑎𝑡𝑖𝑜𝑛s

Question 56

±2𝑆𝐷 =

Answer 56

95.4% 𝑜𝑓 observations

Question 57

±3𝑆𝐷 =

Answer 57

99.7% 𝑜𝑓 𝑜𝑏𝑠𝑒𝑟𝑣𝑎𝑡𝑖𝑜𝑛𝑠

Question 58

- Used as a rejection or warning rule when one control result exceeds the mean +/- 2SD - FOR SCREENING PURPOSE. - Considered as a warning rule, but if the company consider it as a rejection rule, it should be a rejection rule. - Random error

Answer 58

12S rule

Question 59

• If 1 control observation exceeds 𝑥 ± 3s limit • REJECT THE RUN FOR PROBABLE. • Random Error

Answer 59

13s rule

Question 60

• If 2 consecutive control values are greater than 𝑥 ± 2s limit • REJECT THE RUN FOR PROBABLE • Systematic Error.

Answer 60

22s

Question 61

• If the difference between the 2 controls is equal to or greater than 4s. • REJECT THE RUN FOR PROBABLE. • Random Error.

Answer 61

R4s

Question 62

• If 10 consecutive control values falls on one side of the mean. • REJECT THE RUN FOR PROBABLE. • Systematic errors

Answer 62

10x

Question 63

- If 4 consecutive control values are greater than 𝑥 ± 1s limit - REJECT THE RUN FOR PROBABLE - Systematic Error.

Answer 63

41s