The Right Thermometer for Tiny Infants: Rectal Proves Most Reliable
Abstract & Commentary
Source: Callanan D. Detecting fever in young infants: Reliability of perceived, pacifier, and temporal artery temperatures in infants younger than 3 months of age. Pediatr Emerg Care 2003;19:240-243.
Fever in babies is a major cause for parental alarm and frequently leads to ED evaluation. Families and physicians need accurate measurements of body temperature to expedite evaluation of infants thought to have fever, an indicator of possible serious bacterial illness. Callanan analyzed three methods of temperature measurement among babies in an ED population to ascertain performance criteria for means of fever determination.
Two hundred infants younger than 3 months of age were studied at an urban pediatric ED in San Antonio. Parents were queried as to their perception of the presence or absence of fever (perc-T) in their children, regardless of presenting complaint. Each patient then had temperature measurement by three methods: pacifier thermometer (pac-T), temporal artery thermometer (temp-T), and rectal thermometer (rect-T). Fever was defined as temperature exceeding 38.0° C (100.4° F) by rect-T determination.
Based on rect-T determinations in 179 infants, 91% of 23 febrile infants were accurately detected as having fever greater than 38.0° C by tactile perception (perc-T) among parents. Yet 21% of 156 nonfebrile infants also were thought to have fever by parental perc-T estimation. Hence, for the perc-T method, sensitivity was 91%, specificity 79%, positive predictive value (PPV) 39%, and negative predictive value (NPV) 98%.
Pacifier thermometry among 149 infants, 21 (14%) of whom were febrile, revealed a sensitivity of 48%, specificity of 99%, PPV of 91%, and NPV of 92%. Difficulty was encountered with inability or refusal of many infants to suck on the pacifier device for times sufficient to reach endpoints for measurement.
For 187 infants evaluated by temporal artery thermometry, including 23 (12%) febrile patients, sensitivity and specificity of temp-T were 83% and 86%, respectively, while PPV and NPV were 45% and 97%, respectively. The author concludes that parents are accurate in perc-T detection of fever among infants younger than 3 months of age, but that the pac-T and temp-T tools tested in this study are unacceptably variable compared to rect-T measurements.
Commentary by Michael Felz, MD
Unfortunately, the same perc-T method by which parents reliably detected fever also overestimated temperature in one of five infants tested. Pac-T, while attractive to caregivers, is highly dependent on the infant’s willingness to suck on an artificial nipple device for prolonged, sometimes unachievable, periods of time, which sharply lowers sensitivity. The temp-T method, recently available for home use, seems promising based on the ease and rapidity of sweeping the probe across the forehead, but is plagued with misclassification of febrile infants as normal, and healthy infants as febrile, in 15-20% of cases.
My impression of this data is that perc-T still matters, for parents traditionally are the unsurpassed "front line" in recognizing fever in their infants and seeking ED or office evaluation appropriately. This study emphatically demonstrates the tactile reliability of parental detection of fever, with 91% sensitivity. But the pacifier and forehead methods, by comparison, have a long way to go to equal the performance of "mother’s touch" in detecting fever, much as has been the case for axillary and tympanic thermometry devices when tested in young infants.
Rectal thermometry remains the best method of detecting or excluding fever when considering urgent sepsis workups in infants younger than 3 months of age in the ED or office.
At our tertiary care center, ED physicians doggedly insist on rectal temperatures for the tiny tot who feels hot. I further would suggest that fever as indicated by all noninvasive devices for measurement of temperature in tiny babies be accurately confirmed by rectal methodology before proceeding with complete blood count, blood and urine cultures, chest films, lumbar punctures, antibiotics, and/or hospital admission. I suppose you could view the fever-in-infants issue this way: determination of fever requires clinical precision far exceeding a 50-50 coin toss, so in the ED, it is heads (forehead, pacifier methods) you lose, and tails (rectal thermometer) you win.
Dr. Felz, Associate Professor, Department of Family Medicine, Medical College of Georgia, Augusta, is on the Editorial Board of Emergency Medicine Alert.
Callanan analyzed three methods of temperature measurement among babies in an ED population to ascertain performance criteria for means of fever determination.
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