Veterinary Practice Laboratory Unit 1 Chapter 4 The Metric System and Lab Calculations Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Got Math? Veterinary technicians require knowledge and skill at performing a variety of calculations in the clinical laboratory. Reagent solutions may need to be prepared or diluted, samples must be measured and sometimes diluted, and results must be calculated. All of these mathematical operations require that the veterinary technician have a thorough understanding of the metric system, as well as a strong background in basic algebra Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Numbers Abstract Concrete No unit designations Specific unit value (e.g., grams) Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Metric System Most commonly used system in veterinary medicine Based on the powers of 10 Decimal system Three basic units Weight (grams) Volume (liters) Length (meters) Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Powers of Ten Use of prefixes to indicate powers of ten Centi 10-2 Milli 10-3 Micro 10-6 Deca 10-1 Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

General Rules Any number without a number to the left of the decimal point must have a 0 in that place Not .12 But 0.12 Avoid tragic mistakes in dosages Do not add zeros after the decimal numbers Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

International System of Units Derived form the French Le Système International d’Unités Abbreviated SI SI units are designated for seven different types of measurement: length, mass, time, electric current, temperature, luminosity, and quantity In the veterinary clinical laboratory, the SI units of importance are those for mass, temperature, and quantity The SI unit of mass is the kilogram, temperature is reported in kelvin, and quantity as moles Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Dilutions Ratios Amount of one item relative to the amount of another 1:10 dilution of a patient sample combines 10 microliters of sample with 90 microliters of distilled water Results then are multiplied by 10 to yield the correct value Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Serial Dilutions Needed when performing immunologic tests or preparing manual calibration curves on instruments Example Bilirubin contains 20 mg/dL and is diluted 1:5, 1:10, and 1:15; the resulting concentrations of each dilution are 4 mg/dL, 2 mg/dL, and 1 mg/dL, respectively Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Scientific Notation Easy way to handle very large numbers Uses the powers of 10 100 = 0 101 = 10 102 =10 × 10 = 100 Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Steps to Convert to Exponential Form 1. Move the decimal point so that the first term is more than 1 and less than 10 2. The second term is a power of 10 that is equal to the number of times that the decimal point was moved 3. The sign (+ or −) determines the direction in which to move the decimal. The use of + means that the decimal point was moved to the left; the use of − means moved to the right Example: 6,097,000 = 6.097 × 106 Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

pH and Logarithms Used to manipulate very large or small numbers pH A substance with a pH of 6 has an H+ concentration of 10-6 Tidbit – Richter scale also uses logarithms Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Temperature Conversions Celsius is most commonly used in veterinary medicine However, some test kits may refer to Fahrenheit or Kelvin systems for storage, etc. Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Points of Equivalence Absolute zero K = ‒273° C = ‒459.4° F Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Calculations F = 9/5(C + 40) – 40 C = 5/9 (F + 40) – 40 or What is the correct conversion to Fahrenheit of 37° C? Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Summary Math is a must!! Metric system Powers of 10 International system of units Dilutions pH and logarithms Temperature conversions Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.