Researchers in Japan recently published a study in the journal Early Human Development involving 47 newborns, all healthy and between three and four days old. The authors tested salivary biomarkers for hormonal changes in response to pain. Researchers found no such changes in hormone levels leading to the conclusion that salivary biomarkers cannot adequately assess newborn pain.

The heels of newborn participants were lanced for newborn testing. A video was recorded to assess physical signs of pain and heart rate levels were monitored. The video was used to assess pain by two individual experts. The pain was ranked based on the NIP (Neonatal Infant Pain) Scale.

Researchers found that NIP Scale and heart rate were good indicators of newborn pain, but no increase in hormone levels were noted. Salivary biomarkers are not a good means of measuring pain levels in neonates in any clinical setting.

Source: Shibata M, Kawai M, Matsukura T, Heike T, Okanoya K, Myowa-Yamakoshi M. Salivary biomarkers are not suitable for pain assessment in newborns. Early Hum Dev. 2013 Apr 9. pii: S0378-3782(13)00061-3. doi: 10.1016/j.earlhumdev.2013.03.006.