Ward's World Infographics and Guides

Page 1 How to Get an Accurate Temperature Measurement Information compiled by American Diagnostic Corporation (ADC) Step 1: Purchase a high-quality thermometer. Step 2: Remove from package. Step 3: Use the instructions provided. If only it were that easy, right? Well, in some ways, it is. Accurate temperature measurements begin with selecting a reliable brand of thermometer. Most digital stick thermometers and various infrared thermometers (including non-contact and tympanic models that take readings from the ear) are manufac- tured in China and distributed under numerous brand names internationally. However, not all manufacturing facilities in China maintain high standards, and many U.S. importers lack the facilities to test these devices properly. Responsible companies, such as ADC, ensure their digital thermometers are produced by ISO-certified subcontractors. Some even possess their own testing laboratories right here in the U.S. This enables them to conduct random tests on incom- ing shipments to verify compliance with international accuracy standards. For digital stick thermometers, the accuracy stan- dard is ± 0.2°F or 0.1°C (when tested on a water bath), within a temperature range of 98°F to 102.0°F. Only a select few companies perform such rigorous in-house testing. Top research consulting firms often recognize these companies for excellence in quality control. These testing labs are not only used to check their own products but also to evalu- ate competitors' thermometers, often finding that they do not meet specified accuracy standards, do not measure temperature within the required time, or are shipped with expired batteries. But how do you ensure you get accurate measurements with your thermometer, regardless of the brand? It helps to understand temperature measurement and the instrument's limitations. Let's start with a bit about body temperature… What Is Body Temperature? Core temperature is the temperature deep within your body. Most think of normal temperature as 98.6°F, but that can be misleading. (It might not even be "normal" anymore; several recent studies have suggested that human body temperatures have dropped over the last century.) Like other vital signs, including blood pressure, this number merely represents a population average. At the individual level, everyone's body temperature is unique and can vary by about a degree. So it's likely your average body temperature falls more in the 97.6°F to 99.6°F range. In addition, your body temperature varies, not just when you're ill, but at different times of day and depending on certain environmen- tal factors. Age also plays a role, as does site selection (where on your body you take the measurement). The chart included here shows how some of these variables impact temperature ranges. If you take your temper- ature a few times when "healthy," you can get a baseline of your normal temperature. Where Is Temperature Measured on the Body? There are three common sites for temperature measurement using stick thermometers — oral, rectal, and axillary (under- arm) — and three for temperature measurement using an infra- red device — inner ear, forehead, or temporal artery. Stick thermometers report the actual temperature they detect. Infrared thermometers generally don't. Instead, they convert the observed reading to either a core or oral equivalent. Check with the manufacturer of the infrared thermometer to under- stand how their unit works. Digital stick thermometers are offered in universal, oral, or rectal designs. Most use the exact same circuitry, though, and are simply color-coded for control in institutional settings. (So a digital stick thermometer that's coded for oral can, in fact, be used at all three sites with equally accurate results.) True core body temperature is most closely represented by rectal temperature readings. Oral readings tend to be about 1°F cooler. Axillary is another 1°F cooler than that. Some sites make it easier to obtain accurate readings. Rectal is the easiest because it provides excellent surface contact and less opportunity for faulty techniques to influence readings. Oral is second easiest, and axillary the most challenging. + ward ' s science

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