MLS 407 | Laboratory Math

When rounding, if the digit to be dropped is equal to 5, and the preceding digit is odd, what should you do?

The preceding digit is increased by 1

93.35 = 93.4

When rounding, if the digit to be dropped is equal to 5, and the preceding digit is even, what should you do?

The preceding digit is not changed

93.85 = 93.8

Pico (p)

• 10^-12

• picrogram (pg)

Nano (n)

• 10^-9

• nanogram (ng)

Micro (u)

• 10^-6

• microliter (uL) and microgram (ug)

Milli (m)

• 10^-3

• milligram (mg) and milliliter (mL)

Deci (d)

• 10^-1

• deciliter (dL)

Kilo

• 10³

• kilogram (kg)

Convert between Fahrenheit, Kelvin and Celsius

F = 32 + (C x 9/5)

C = 5/9 x (F - 32)

K = C + 27C

What is a dilution?

Reduces the concentration of a solute in a solution

Ratios and an expression of the relative concentrations of the components in a final solution

(1 part original solution : total parts final solution)

What is a simple dilution?

A simple dilution is prepared by adding a specific volume of diluent (solvent) to a specific volume of concentrated solution

Is a 1:1 dilution ratio, diluted?

No, it is referred to as a “neat” specimen

Dilutions are generally expressed in terms of ___ numbers and are reduced to the ___ common denominator

whole; lowest

Dilution Factor

The reciprocal of the dilution made

T/F: A dilution is not necessary to measure the analyte in the concentrated solution

False, it is required

T/F: Analysis of the diluted sample yields an accurate measurement of the analyte in the diluted sample

True

The test result obtained from the diluted sample must be “corrected” for the dilution using the ____ ____

dilution factor

Diluents

The neutral solutions that must not interfere with the analysis or the analyte being measured

Examples: reagent water, distilled water, deionized water, buffer, zero standard

What factors play a role in choosing a diluent?

• Matrix of test solution

• Analyte being measured

• Test method

• Manufacturer’s recommendation

Explain how to prepare a 1:3 dilution of a patient specimen using 0.1 mL of specimen and saline (diluent)

1 part solute (0.1 mL) to 2 parts solvent (0.2 mL saline)

How do you set up and label tubes for a dilution?

1. Label patient specimen tube

2. Set up diluent tube

3. Label dilution tube with patient name and dilution ratio

Explain how to prepare a 1:3 dilution of a patient specimen using 0.3 mL of specimen and saline (diluent)

Transfer 0.3 mL of patient specimen into a labeled test tube containing 0.6 mL saline; mix well

Explain how to prepare the 1:5 dilution using 0.05 ml of patient specimen

Transfer 0.05 mL of patient specimen to a labeled tube containing 0.20 mL diluent

A result obtained for a 1:5 dilution is 120 mg/dL. What is the final test result to be reported to the patient medical record?

Dilution = 1:5 = 1/5

Dilution factor = 5

120 mg/dL x 5 = 600 mg/dL

T/F: The concentration of a stock standard solution is known

True

How do you calculate the concentration of the working standard?

Multiply the concentration of the stock standard by the dilution (ratio expression)

A ‘stock’ standard has a concentration of 1000 mg/dL. The procedure indicates we need to prepare a ‘working’ standard by diluting the stock standard 1:100 using saline. What is the concentration of the ‘working’ standard?

1000 mg/dL x 1/100

10 mg/dL

The concentration of the stock standard is 5000 mg/dL. We need to prepare a working standard with a concentration of 50 mg/dL. What dilution of the stock standard needs to be prepared to achieve the desired concentration of working standard?

Explain how you will prepare this dilution using 0.1 mL of stock standard and the proper diluent

1:100 dilution

Transfer 0.1 mL of stock standard into a test tube containing 9.9 mL diluent and mix well

How would you set up and label tubes during a working standard dilution?

1. Tube labeled “stock standard”

2. Tube with diluent

3. Tube labeled “working standard”

What does a X-fold serial dilution mean?

A dilution happened X amount of times sequentially

How should you label tubes when performing a serial dilution?

Each tube should have a number and the dilution (ratio)

When preparing dilutions, especially serial dilutions, we need to be able to calculate and document the following information:

• Tube dilution

• Final tube dilution

• Substance dilution

Prepare a 1:3 dilution of a patient specimen using 0.2 ml of specimen and saline. Calculate the tube dilution, final tube dilution and substance dilution in each tube

Tube dilution: 1:3

Final tube dilution: 1:3

Substance dilution: 1:3

Prepare a 1:2 dilution; then prepare a 1:5 dilution on the 1:2 dilution. Use 0.1 mL sample. Then calculate the tube dilution, final tube dilution, and substance dilution

1:2 tube

• Tube dilution: 1:2

• Final tube dilution: 1:2

• Substance dilution: 1:2

1:5 tube

• Tube dilution: 1:5

• Final tube dilution: 1:10

• Substance dilution: 1:10

Titer

A way of expressing concentration

The reciprocal of the dilution that is required to produce a defined outcome in a defined system

Titer testing employs ___ ___ to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as ___ or ____

serial dilutions; positive; negative

The titer corresponds to the ____ dilution that still yields a ____ reading

highest; positive

What is the endpoint titer?

The reciprocal of the highest analyte (concentration) dilution that gives a reading above the cutoff

T/F: When reporting results, you should always follow your laboratory’s SOP

True

Titers are performed to:

• Confirm vaccination

• Verify past infection

• Determine strength of immune response

• Evaluate effectiveness of treatment

The highest dilution that gives a positive reaction is defined as the ______ titer.

Endpoint

10 g/L = ________ mg/dL

1000

20 uL = ______ mL

0.02

Which of the following represents a correct dilution calculation?

A. 0.1 mL sample added to 0.5 mL diluent = 1:5 dilution

B. 0.3 mL sample added to 0.3 mL diluent = 1:2 dilution

C. 0.050 mL sample added to 0.1 mL diluent = 1:2 dilution

D. 0.1 mL sample added to 1.0 mL diluent = 1:10 dilution

B

A 40% solution is diluted 1:4. The final concentration of the diluted solution is:

Correct answer:

10%

A test sample was diluted 1:100. The result of the diluted specimen was 45 g/dL. Which of the following is the correct value to be reported?

A. 4.5 g/dL

B. 45 g/dL

C. 450 g/dL

D. 4500 g/dL

D

What is the dilution prepared in each tube of a 3-fold serial dilution?

1:3

A 4-fold serial dilution using 0.1 mL of specimen is performed on 5 tubes. How much diluent is in each tube?

0.3 mL

You have a series of 5 tubes with 1 mL of diluent in each tube. One mL of serum is added to the first tube and mixed well. Then 1.0 mL from tube 1 is transferred to tube 2 and mixed well. This process is repeated through the remaining tubes in the series. What is the substance dilution in tube #3?

1:8

A titer endpoint is defined as the ____________.

Highest dilution yielding a positive reading

A 3-fold serial dilution in 5 tubes is prepared on a specimen to determine the antibody titer. A reaction was noted in tubes 1 through 4, but not in tube 5. What is the antibody titer of the specimen?

1:81 or 81