Abstract. As a specific biomarker in neonatal hypoxic-ischemic encephalopathy (HIE), the measurement of neuron-specific enolase (NSE) has been advocated as a predictor of outcome in neurological injury. However, the measured levels of NSE may be influenced by hemolysis. In the current study, the change in the concentration of NSE in serum was measured by chemiluminescence prior to and following the addition of individual frozen and thawed red blood cells from 86 neonates that were collected within 24 h of birth. The changes in the concentration of NSE were compared with the changes in the concentration of hemoglobin (Hb), measured by the hemoglobin cyanide (HiCN) method, to establish a correction formula. The performance of the correction formula was evaluated by comparing the corrected concentration of NSE using the individual constants and the correction formula. The average individual constant of NSE from the 86 hemolyzed neonatal serum samples was 25.15±3.94 mg/g Hb. The concentration variation between NSE and Hb in neonatal sera could be described by the equation ΔNSE serum =1.8594+24.0670 xΔHb HiCN (r²= 0.8045, P<0.001). There was no statistically significant difference in the NSE corrected results between the individual constant group and the correction formula group (Z=-1.645, P=0.100). The linear regression formula of Hb measured with the instrumental method compared with the HiCN method was Hb instr = 0.9816xHb HiCN +0.5596 (r²= 0.9924, P<0.001). Based on these regression analyses, the correction formula for NSE in hemolyzed neonatal serum was determined as NSE corr =NSE meas -24.0670xHb HiCN -1.8594 or NSE corr = NSE meas -24.5181xHb instr +11.8609. In conclusion, hemolysis has a substantial influence on the accurate measurement of NSE in neonatal serum samples. For hemolyzed neonatal serum samples, correcting the NSE results using a correction formula is essential to evaluate the severity of neonatal hypoxic ischemic encephalopathy.
IntroductionHypoxic-ischemic encephalopathy (HIE) secondary to perinatal asphyxia remains a major cause of neonatal mortality and morbidity worldwide (1,2). The incidence of HIE ranges from 1 to 3 per 1,000 full-term infants and is present in almost 60% of premature newborns (3-5). Approximately 15-20% of affected newborns succumb within the postnatal period, and an additional 25% develop severe and permanent neuropsychological handicaps, including cerebral palsy, seizures, visual impairment, mental retardation, learning disabilities and epilepsy (5).Neuron-specific enolase (NSE) belongs to the family of enolase enzymes present in all tissues and organisms capable of glycolysis (6). Enolases consist of three subunits (α, β, and γ) encoded by separate genes. These subunits may combine to form five different isoenzymes: αα, αβ, αγ, ββ and γγ (6). NSE, comprised of γγ homodimers and αγ heterodimers, is widely distributed in central nervous system neurons and amine precursor uptake and decarboxylation cells (7). As a marker of neuronal cell death, the serum concentration of N...