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Thank you for your excellent series of articles on management of the jaundiced newborn in your May 2005 issue. Regarding laboratory tests to work up secondary causes of hyperbilirubinemia: G6PD is identified numerous times as an important and often overlooked cause of elevated bilirubin in certain ethnic groups. We are taught, however, that, in the setting of acute hemolysis, the population of red blood cells with a quantitatively low level of enzyme may be reduced. What is the rate of false negative screening tests in the neonatal period? Should this screening test be repeated at a later point in indicated patient populations to definitively rule out this cause?
Jeffrey Zaref, MD, MPHFramingham, Mass.
Author reply: As Dr. Zaref points out, older RBCs contain less enzyme than younger cells and are, therefore, at greater risk of hemolyzing. In the presence of acute hemolysis, G6PD levels (in the remaining younger RBCs) can be normal or near normal and could obscure the diagnosis of G6PD deficiency. A normal G6PD level in a hemolyzing newborn, therefore, does not rule out G6PD deficiency1; if G6PD deficiency is strongly suspected, a repeat measurement should certainly be obtained when the infant is 3 months old. On the other hand, in the steady state, screening tests are quite accurate and identify all G6PD-deficient males2 (no false-negative results). In female heterozygotes, however, screening is not as accurate.
1. Beutler E: Glucose-6-phosphate dehydrogenase deficiency. Blood 1994;84:3613
2. Kaplan M, Leiter C, Hammerman C, et al: Comparison of commercial screening tests for glucose-6-phosphate dehydrogenase deficiency in the neonatal period. Clin Chem 1997;43:1236
Congratulations to Dr. Maisels for his review of neonatal jaundice and to Drs. Bhutani, Johnson, and Keren for their article on preventing kernicterus. The emphasis on timing of bilirubin rise is crucial. A chart of the newborn's age in hours simplifies management.
I have taught residents and medical students to:
1.Ask about feedings or observe breastfeeding, or feed the baby themselves. A healthy newborn has a dynamite sucking reflex!
2.Observe the baby's arms. A healthy newborn keeps elbows flexed and fists clenched and up like a boxer.
The picture on the cover of the May 2005 issue of Contemporary Pediatrics shows a jaundiced newborn with thighs, knees, and left arm flexed normally, but the right elbow is extended. Palpation of the right clavicle for fracture and checking Moro reflex would produce pronation of the right forearm if Erb's paralysis is present.
Again: Timing. Timing. TIMING!
Myron M. Nichols, MDHonolulu, Hawaii
Before the first "official" AAP guidelines regarding the management of the jaundiced newborn were issued in 1994, pediatricians were taught to be "vigintiphobes" and used phototherapy aggressively to prevent the bilirubin level from rising to 20 mg/dL-at which point exchange transfusion would be necessary to prevent kernicterus. As a result, in the 1980s, we learned to use home phototherapy to facilitate the treatment of newborn jaundice. Parents and pediatricians favored this home-care approach-it was safe and effective, allowed parents to comfort and nurture their newborn in a familiar environment, and cost only a fraction of comparable care delivered in a hospital. When the AAP relaxed the thresholds for phototherapy and exchange transfusion, however, in the 1994 practice parameter (i.e., healthy term infants over 72 hours of age should have phototherapy starting at 20 mg/dL and an exchange transfusion at 25 mg/dL), we were "vigintiphobes" no longer.
Over the next decade, the new thresholds resulted in fewer healthy term babies receiving phototherapy (at home or in the hospital). As a result, many home-care companies gradually discontinued or downsized their home phototherapy program. Insurance companies ratcheted down the reimbursement for medical home-care services, to a point at which-today-it is not cost effective for most home-care companies to provide home phototherapy.