Quantitative effects of bilirubin structural photoisomers on the measurement of direct bilirubin via the vanadate oxidation method.

BACKGROUND: Exposing blood serum samples to ambient white light-emitting diode (WLED) light may accelerate bilirubin photoisomer production. We previously demonstrated the quantitative effect of bilirubin configurational isomers (BCI) on direct bilirubin (DB) value using the vanadate oxidation method. However, the effects of bilirubin structural photoisomers (BSI) remain unclear. METHODS: In Study 1, the relationship between WLED irradiation time and BSI production was examined. Serum samples from five neonates were irradiated with WLED light for 0, 10, 30, 60 and 180 min. Bilirubin isomer concentration and BSI production rates were calculated. In Study 2, we performed quantitative investigation of BSI effect on DB values: Differences in DB, BCI and BSI values before and after irradiation were calculated as ⊿DB, ⊿BCI and ⊿BSI, respectively. Assuming the coefficient of BCI affecting DB values was 'a', relational expression was ⊿DB = a*⊿BSI + 0.19*⊿BCI. Serum samples from 15 neonates were irradiated with green LED light for 10 and 30 s. The respective bilirubin isomer levels were measured, and the coefficient was derived. RESULTS: In Study 1, the median BSI production rate was 0.022 mg/dL per min in specimens with an unconjugated bilirubin concentration of 10.88 mg/dL. In Study 2, assuming that ⊿DB-0.19*⊿BCI was Y and ⊿BSI was X, the relational expression was Y = 0.34X-0.03 (R2 = 0.87; p < .01) and a = 0.34. CONCLUSIONS: Under ambient WLED light, serum sample generated 1.3 mg/dL BSIs in 1 h. Approximately 34% (0.44 mg/dL) of BSI concentrations was measured as DB when using the vanadate oxidation method according to the above equation.

Green light-emitting diode phototherapy for neonatal hyperbilirubinemia: Randomized controlled trial.

BACKGROUND: The main photochemical pathway in phototherapy for neonatal hyperbilirubinemia is the production and elimination (in bile or urine) of cyclobilirubin, which is a structural photoisomer of bilirubin, and which is most efficiently produced by green light. Green light-emitting diode (LED) phototherapy, however, has not been evaluated in the clinical setting because it is not recommended in American Academy of Pediatrics guidelines. We therefore compared the efficacy of green LED phototherapy and blue LED phototherapy in patients with neonatal hyperbilirubinemia. METHODS: In this prospective randomized controlled trial, neonates with hyperbilirubinemia were randomly allocated to a green LED or blue LED phototherapy group. Both groups underwent 24 h of phototherapy, and blood was sampled before and after 24 h of phototherapy. Total serum bilirubin (TSB) was measured using enzymatic methods and bilirubin photoisomers were measured on high-performance liquid chromatography. RESULTS: Thirty-four infants were randomized (green, n = 16; blue, n = 18). TSB decreased significantly from 15.3 ± 1.5 to 13.9 ± 1.5 mg/dL in the green LED group (P < 0.01) and from 16.2 ± 1.3 to 14.5 ± 1.7 mg/dL in the blue LED group (P < 0.01) after 24 h of phototherapy. No significant difference was found in TSB reduction after phototherapy between the groups. CONCLUSIONS: Both light sources produced a significant reduction in TSB, indicating clinical effectiveness.