CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
so than with the English system. For example, the technician or technologist might
need to know how many milligrams are in grams, or a fraction of a gram, since
the measurement may involve a value of less than a gram. The prefix milli- literally
means “one-thousandth.” For example, 700 milligrams (mg) would indicate 700
thousandths of a gram, which is 70% of a gram, since 700/1,000 equals 70%.
To convert measurements from a smaller unit to a larger unit, such as milligrams
to grams (weight), the decimal in the original unit would be moved to
the left. For example, because there are 1,000 milligrams in a gram (1 mg =
.001), the decimal would be moved three places to the left to indicate 1 gram.
A value of 1,200 mg, then, could be converted to grams by moving the decimal
three places to the left from the end of 1,200 to make the value 1.2 grams.
To convert measurements from a larger unit to a smaller unit, such as
liters to milliliters (volume), the decimal would be moved to the right. An
example would be that of the conversion of 3.5 liters to milliliters (mL) by
moving the decimal to the right three places: 3.5 L to 3500 mL. One should
begin to remember some of the basic names and abbreviations used for the
various units, such as the designation mL for milliliter, which is also synonymous
with a cubic centimeter (cc). Pipettes are devices designed in most cases
for measuring liquids in milliliters. Reagents or chemicals used to test for certain
components of blood are measured in milliliters or fractions of milliliters.
Patients’ samples are much smaller in newer procedures and are measured in
thousandths of milliliters called microliters (μL).
Converting mg/dL to mmol/L or from mmol/L to mg/dL is often necessary
when the clinician to whom the result is reported requires it. Certain countries
use mmol/L instead of mg/dL. To get the equivalent mmol, you can multiply, for
instance, a glucose value in mg/dL by the conversion factor of 0.05551 (example:
110 mg/dL × 0.05551 = 6.1 mmol/L) (Table 9-3). Or, you can use an easier
but less precise way by dividing the mg/dL value by 18 to get the equivalent
number in mmol/L (example: a glucose of 110 mg/dL will be divided by 18 = 6.1
mmol/L). Factors for converting from mg/dL to mmol/L or vice versa require a
different factor for each analyte tested for.
Table 9-3 Conversion Factors from mg/dL to mmol/L ( for Glucose Only)
mmol/L mg/dL mmol/L mg/dL mmol/L mg/dL
0.06 1 6.7 120 16.0 288
0.28 5 7.0 126 16.6 300
0.55 10 7.2 130 17.0 306
1.0 18 7.5 135 18.0 325
1.5 27 7.8 140 19.0 342
NOTE: These factors are for glucose only. Other analytes will be entirely different.
Converting English Units to Metric Units
In the medical laboratory it is often necessary to convert English units to metric
units to complete an equation. Table 9-4 is an easy-to-understand reference
for these conversions. There are often conveniently located charts in medical
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