HEM Quality Systems

Question 1

QC monitors the __ quality and accuracy of a method

Answer 1

QC monitors the ANALYTICAL quality and accuracy of a method

Question 2

Define accuracy. List examples of how it is assessed.

Answer 2

The degree a measured value is from the true value:
- control sample
- compare results to results of a reference method (gold standard)
- compare results to a reference lab

Question 3

Define precision. How is it assessed ?

Answer 3

How well a measured value can be replicated:
- expressed as SD or CV

Question 4

Formula for SD

Answer 4

√(Σ|x- x̄|² /n)

Question 5

A large SD indicates what ?

Answer 5

A large SD indicates IMPRECISION of the method: random error

Question 6

Formula for CV

Answer 6

(SD/ x̄) x 100

Question 7

When is CV used over SD when comparing precision of two methods ?

Answer 7

• comparing methods with different units
• comparing methods with different means
• establishing comparable limits of allowable variation at different concentration ranges ie. CV= 5% of a patient result (100 g/L) means the true value is between 95 and 105 g/L (± 5%)

Question 8

What is “Bull’s Moving Averages” used for ?

Answer 8

• monitors whether instrument results are shifting/ drifting from average indices of a patient pop’n
• cannot detect within-run errors and less sensitive than other methods to detect shifts/ trends

Question 9

Define systematic error

Answer 9

Systematic:
- loss of accuracy = change in mean but not SD
- CONSTANT or PROPORTIONAL
- result in shifts/ trends
- associated with miscalibration, reagent and instrument deterioration

Question 10

Define random error

Answer 10

• accidental and lack a pattern
• loss of precision = large SD
• associated with bubbles, inadequate mixing, unstable instrumentation, skill diff in pipetting
• may be detected by delta checks

Question 11

Differentiate shift vs trend on a control chart

Answer 11

Shift: seven points above OR below the mean

Trend: seven points in an upward/ downward direction

Question 12

1(2S) rule

Answer 12

1 result exceeds 2 SDs from the mean; most likely a “false-alert”

Question 13

1(3S)

Answer 13

1 result exceeds 3 SDs from the mean; random errors

Question 14

2(2S)

Answer 14

• 2 consecutive results exceed 2 SDs from the mean; systematic error
  OR
• 2 different QC specimens run at the same time exceed 2 SDs from the mean; systemic error

Question 15

2 of 3(2S)

Answer 15

2 results from 3 different QC specimens run at the same time exceed 2 SDs from the mean on the SAME DIRECTION; systematic error

Question 16

R(4S)

Answer 16

• 2 consecutive results have a RANGE that is > 4 SDs; random error
  OR
• 2 different QC specimens ran at the same time produce results that exceed 4 SDs from the mean; random error

Question 17

8(1S)

Answer 17

8 consecutive values exceed 1 SD from the mean in the SAME DIRECTION; systemic error

Question 18

10(X)

Answer 18

10 consecutive values exceed 1 SD in the SAME DIRECTION; systemic error

Question 19

2 of 3(2S)

Answer 19

2 results from 3 different QC specimens run at the same time exceed 2 SDs from the mean on the SAME DIRECTION; systematic error

Question 20

Define delta check; What kind of error does it help detect ?

Answer 20

• computer compares current result to the previous
• flags results that are significantly different
• helps ensure sample integrity and detect clerical errors

Question 21

Define “critical value” for a sample; what follow-up steps are done ?

Answer 21

1. review testing conditions and specimen integrity (no instrument error, clots, mislabeled samples)
2. check previous value if critical is known or new
3. verbally report results to appropriate party and document log

Question 22

What is an external quality control program ?

Answer 22

• governing bodies sends out a control sample for labs to test
• tested using regular lab workflow
• inter-laboratory communication is prohibited before reporting results

Question 23

Define Non-conforming event (NCE). What form is filled out when an NCE occurs in the Edmonton zone ?

Answer 23

• occurrence management
• a system used to report, investigate, and correct incidents, errors or near misses that affect lab results or patient care
• RLS (Reporting and Learning System) form for patient safety is filled out

Question 24

Which of the following would be the correct procedure for handling external proficiency testing samples?

a.
Only the most experienced technologists run the sample

b.
Contact and consult other laboratories in the region to compare results before reporting

c.
Perform the analysis in triplicate to ensure the correct value is obtained

d.
Ensure any Q.C problems are resolved prior to running the proficiency testing samples

Answer 24

d.
Ensure any Q.C problems are resolved prior to running the proficiency testing samples

Question 25

What do hematology controls primarily check for? a. Accuracy of a method b. Precision of a method c. Pre-analytical error d. Co-efficient of variation

Answer 25

a. Accuracy of a method

Question 26

Which of the following is included in the category of 'quality assurance'? a. Ensuring pre-analytical variables such as specimen transport are controlled b. Ensuring documents and records management departments are following accreditation guidelines c. Ensure all laboratory personnel are registered with the CMLTA d. All of the above

Answer 26

a. Ensuring pre-analytical variables such as specimen transport are controlled