Speakman E D, Boyd J C, Bruns D E
Department of Pathology, University of Virginia Health Sciences Center, Charlottesville 22908.
Clin Chem. 1995 Mar;41(3):458-61.
Because of the potential for methemoglobinemia during nitric oxide therapy in newborns, methods are needed to accurately quantify methemoglobin (MetHb) in the presence of the high concentrations of fetal hemoglobin (Hb F), bilirubin, and lipids seen in these patients. Spectral differences between fetal and adult Hbs invalidate assumptions of conventional multiwavelength Hb photometry, so we evaluated an "overdetermined" system (Ciba-Corning Model 270), in which absorbances at seven wavelengths are measured to quantify four Hb derivatives. Adult and umbilical cord blood (Hb F 96%) samples were prepared to contain known MetHb fractions. Measured MetHb was linear in cord blood to > or = 15% MetHb. Within-run precision (CV) was < 2.2% (n = 10) at each of seven MetHb fractions between 5% and 100%. Measured (y) and expected (x) MetHb fractions in cord blood were in good agreement (y = 1.0200x + 0.100, Sylx = 0). Added bilibrubin (200 mg/L serum) and lipid (30 g/L) did not interfere. No significant differences were seen for adult and cord blood samples with identical MetHb fractions (P = 0.72), whereas a significant difference was noted with an exactly determined system (P = 0.0033). At clinically relevant MetHb fractions (< 15%), a trend towards increased values in cord blood was noted with an exactly determined system (y = 1.0520x + 0.7600). We conclude that this overdetermined system measures MetHb accurately in samples from patients with large concentrations of Hb F.
由于新生儿一氧化氮治疗期间存在高铁血红蛋白血症的可能性，因此需要一些方法来在这些患者中存在的高浓度胎儿血红蛋白（Hb F）、胆红素和脂质的情况下准确量化高铁血红蛋白（MetHb）。胎儿血红蛋白和成人血红蛋白之间的光谱差异使传统多波长血红蛋白光度法的假设无效，因此我们评估了一种“超定”系统（Ciba-Corning 270型），其中测量七个波长处的吸光度以量化四种血红蛋白衍生物。制备成人和脐带血（Hb F 96%）样本以包含已知的MetHb组分。在脐带血中，测量的MetHb在MetHb含量大于或等于15%时呈线性。在5%至100%的七个MetHb组分中的每一个处，批内精密度（CV）均小于2.2%（n = 10）。脐带血中测量的（y）和预期的（x）MetHb组分高度一致（y = 1.0200x + 0.100，Sylx = 0）。添加的胆红素（200 mg/L血清）和脂质（30 g/L）不产生干扰。对于具有相同MetHb组分的成人和脐带血样本，未观察到显著差异（P = 0.72），而在精确测定系统中则观察到显著差异（P = 0.0033）。在临床相关的MetHb组分（< 15%）下，精确测定系统显示脐带血中的值有增加趋势（y = 1.0520x + 0.7600）。我们得出结论，这种超定系统能够准确测量来自高浓度Hb F患者样本中的MetHb。
