Serum and Specimen Collection Techniques

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Questions and Answers

What defines serum as compared to plasma?

Serum is plasma without clotting factors. (correct)

Serum contains clotting factors.

Serum is obtained from anticoagulated blood.

Serum includes blood cells.

What is the primary method used to obtain serum?

Letting blood clot and centrifuging the sample. (correct)

Adding preservatives before centrifugation.

Centrifugation of blood containing anticoagulants.

Directly extracting from a venipuncture.

Which temperature range is recommended for storing serum if immediate testing cannot be performed?

Room temperature

Above 10°C

Below 0°C

Between 2°C and 8°C (correct)

What process is needed to inactivate complement activity in serum before certain tests?

Heating to 56°C for 30 minutes. Signup and view all the answers

Which of the following statements about dilution is correct?

Dilution requires the solute and the diluent. Signup and view all the answers

What is serology primarily concerned with?

The study of serum for diagnostic purposes. Signup and view all the answers

How should blood be collected to avoid affecting test results?

Aseptically by venipuncture into a sterile tube. Signup and view all the answers

What is the consequence of hemolysis in serum samples?

It may affect the test results negatively. Signup and view all the answers

What is the titer of ANA based on the given results?

8 Signup and view all the answers

In an ideal clinical test, what do true positives represent?

Patients with the disease testing positive Signup and view all the answers

What formula is used to calculate the sensitivity of a test?

Sensitivity (%) = (True Positives / (True Positives + False Negatives)) × 100 Signup and view all the answers

What does a highly specific test indicate?

It accurately measures a specific substance without interference Signup and view all the answers

Given the example results, how many true negatives were recorded?

20 Signup and view all the answers

In the context of clinical testing, what is a false negative?

A patient with the disease tests negative Signup and view all the answers

Based on the given patient results, how can you calculate the specificity of the test?

Specificity (%) = (True Negatives / (True Negatives + False Positives)) × 100 Signup and view all the answers

What was the total number of patients tested in the example?

200 Signup and view all the answers

What calculation would you perform to find the volume of serum needed for a 1/20 dilution in a total volume of 2 mL?

Vs = 2 / 20 Signup and view all the answers

If you have 0.1 mL of serum and need to prepare a 1:5 dilution, how much diluent is necessary?

0.2 mL Signup and view all the answers

How much diluent would you use if you wish to make a 1:10 dilution by adding 0.1 mL of serum?

9.9 mL Signup and view all the answers

What is the dilution factor in a two-fold serial dilution?

1/2 Signup and view all the answers

To prepare 50 mL of a working reagent at a 1X concentration from a 10X concentrated stock, how much stock reagent is required?

25 mL Signup and view all the answers

What does the titer indicate in serology?

The highest dilution showing a positive reaction Signup and view all the answers

In a ten-fold serial dilution, what is the dilution factor applied at each step?

1/10 Signup and view all the answers

What results from using a first dilution to prepare a second dilution in serial dilution?

Uniform dilution factor across steps Signup and view all the answers

Study Notes

Serum

Serum is the liquid component of blood that does not contain blood cells or clotting factors (fibrinogen).
Clotting factors are present in plasma but not serum.
To obtain serum, allow a blood sample to clot in a clean plain tube, then centrifuge the sample, and separate the clear supernatant.
To obtain plasma, collect the blood sample in a tube containing an anticoagulant (like heparin or EDTA), then centrifuge and collect the supernatant.
Serology: the study of serum.
Serology generally refers to identifying specific antigens or antibodies in the serum.

Specimen Collection, Preparation, and Storage

Blood is collected aseptically via venipuncture into a clean, dry, sterile tube.
Hemolysis should be avoided as it can impact test results.
Fresh serum is generally ideal for testing.
Serum can be stored between 2°C and 8°C for up to 72 hours if immediate testing is not possible.
If testing is delayed further, freeze serum at -20°C or lower.

Inactivation of Complement

Complement inactivation is the process that destroys complement activity in the serum.
Complement can interfere with certain test reactions.
In these tests, complement must be inactivated in the sample before testing.
Heat inactivation can be achieved by heating the sample to 56°C for 30 minutes.

Dilution

Most serological tests require reagent dilution prior to the test.
Many tests require dilution of the serum before performing the test.
Dilution is expressed as a ratio or fraction (e.g., 1:10 or 1/10).
This means the solute was diluted 10 times (10X) by mixing 1 volume of solute with 9 volumes of diluent.
In serological tests, serum samples are often diluted in normal saline (NS), phosphate-buffered saline (PBS), or a diluent provided by the manufacturer.
Dilution = Total volume (Vt) = Volume of solute (Vs) + Volume of diluent (Vd)

Serial Dilution

Serial dilution is a series of dilutions where the dilution factor remains consistent at each step.
The concentration decreases by the same quantity in each consecutive step.
A first dilution is prepared, then this dilution is used to create a second dilution, and so on.
Two-fold serial dilution: The serum is diluted by a factor of ½ in each step.
Ten-fold serial dilution: The serum is diluted by a factor of 1/10 at each step.

Titer

The titer is the reciprocal of the highest dilution in which a positive reaction occurs.
It is used as an indicator of antibody strength.
To determine the titer, a two-fold serial dilution is conducted first.
Each dilution is then tested.
The titer corresponds to the reciprocal of the highest dilution still yielding a positive result.

Test Parameters

Many clinical tests are used to confirm or disprove the presence of a disease.
An ideal test would have 100% sensitivity and 100% specificity:
- True positive: The patient has the disease, and the test is positive.
- True negative: The individual does not have the disease, and the test is negative.
However, most tests are not ideal:
- False positive: The individual does not have the disease, but the test is positive.
- False negative: The patient has the disease, but the test is negative.

Sensitivity vs Specificity

Sensitivity: The proportion of people who have a disease or condition and have a positive test result.
- Sensitivity (%) = (True Positives / (True Positives + False Negatives)) x 100
- A highly sensitive test can detect small amounts of the substance being measured, producing a positive result even with low concentrations.
Specificity: The proportion of people who do not have a disease or condition and have a negative test result.
- Specificity (%) = (True Negatives / (True Negatives + False Positives)) x 100
- A highly specific test measures only the substance it's designed to measure, not interfering substances.

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Description

This quiz covers essential information regarding serum, its components, and the collection methods used in laboratory settings. Learn the differences between serum and plasma, the significance of serology, and best practices for specimen collection and storage. Test your knowledge and ensure accurate laboratory results.