Respiratory Biochemistry

Question 1

<p>Define the term accuracy</p>

Answer 1

<p>How close the result is to the actual value</p>

Question 2

<p>Define the term precision</p>

Answer 2

<p>The closeness of the repeat results</p>

Question 3

<p>How can precision be calculated?</p>

Answer 3

<p>The expected results of internal quality control (IQC) samples are known and the actual results are compared with the previous results</p>

Question 4

<p>What happens with external quality control (EQC) samples?</p>

Answer 4

<p>- Circulated by an external lab to lots of NHS biochemistry labs

- expected results are not known to staff when they are analysing the samples
- results are circulated and method mean is usually taken as true result</p>

Question 5

<p>What is a reference interval?</p>

Answer 5

<p>On a graph, includes the middle 95% of the population sampled</p>

Question 6

What does it imply about results that fall in the 2.5% tails of the population out of the reference interval?

Answer 6

An abnormal result
- does not necessarily signify pathology but further away it is from the 95% the more likely it is to represent pathology

Question 7

Specificity

Answer 7

• Percentage of people without MI who have a normal (negative) test
• Measure of how good the test is at identifying health

Question 8

What is the positive predictive value (PPV)?

Answer 8

The percentage of people with a positive test who have the disease

Question 9

How do you calculate the positive predictive value?

Answer 9

TP/(TP+FP)

Question 10

What is the negative predictive value (NPV)?

Answer 10

The percentage of people with a negative test who don’t have the condition

Question 11

How do you calculate the positive predictive value?

Answer 11

TN/(TN+FN)

Question 12

What is prevalence?

Answer 12

The percentage of the population with the disease

Question 13

What can the three possible sources of random variation be broadly divided into?

Answer 13

• pre-analytical variation
• analytical variation
• intrinsic biological variation

Question 14

Why does hydrogen ion concentration ([H+], pH) need to be regulated?

Answer 14

• 60 millimil H+ are produced by metabolism daily
• Need to excrete most or all of this (in urine)
• So normal urine is profoundly acidic
• [H+] is 35 to 45 nanomol/L so very tight

Question 15

What is pCO2?

Answer 15

The respiratory component

- Primary change is in pCO2

Question 16

What is HCO3-?

Answer 16

The metabolic component

- The primary change is in HCO3-

Question 17

What is an Acidosis?

Answer 17

• Increase in hydrogen conc

- Process tending to cause an increase in hydrogen conc

Question 18

What is an alkalosis?

Answer 18

• Decrease in hydrogen conc

- Process tending to cause a decrease in hydrogen conc

Question 19

What is respiratory acidosis and alkalosis?

Answer 19

• Increase/decrease in hydrogen due to increase/decrease in pCO2

Question 20

What is metabolic acidosis and alkalosis?

Answer 20

• Increase/decrease in hydrogen due to increase/decrease in HCO3-

Question 21

How do you compensate for acid-base distrubances?

Answer 21

• when you’ve got too much H+, the lungs blow off CO2

- When you’ve got too much CO2, the kidneys get rid of H+

Question 22

What does compensation do?

Answer 22

Allows the body to let the reactions opposite continue

Stops the build up of primary problem

Question 23

What can cause alkalosis?

Answer 23

• hysterical overbreathing
• mechanical over-ventilation
• raised intercranial pressure

Question 24

What can cause acidosis?

Answer 24

• choking
• bronchhopneumonia
• COAD

Question 25

What is within-subject biological variation?

Answer 25

Calculating the additional variation within the subject or patient that is not due to random pre-analytical or analytical factors - can work out the amount of change between serial results