Transcutaneous bilirubin measurement is a useful screening tool for neonatal hyperbilirubinemia, but it has some limitations and sources of variability. Therefore, any bilirubin screening result obtained must be confirmed by a diagnostic method before treatment.

Choice A is wrong because initiating phototherapy without confirming the bilirubin level could expose the newborn to unnecessary treatment and potential adverse effects.

Choice C is wrong because increasing hydration by feeding more frequently may not be sufficient to lower the bilirubin level if it is too high or if there are other causes of jaundice.

Choice D is wrong because reassuring the parent that this is a normal finding could delay the diagnosis and treatment of severe neonatal hyperbilirubinemia, which can lead to serious complications such as kernicterus spectrum disorders.

Normal ranges for transcutaneous bilirubin measurement vary depending on the device used, the skin pigmentation, and the postnatal age of the newborn. However, a general guideline is that a measurement of 16 mg/dL at 48 hours of age is above the 95th percentile and warrants further investigation.