Specimen collection: The urine specimen must be collected within 6 hours of birth.
Chemical analysis:
(1) The authors used NMR spectroscopy to measure parts per million of lactate and creatinine in the urine.
(2) Since a ratio for the number of molecules is used, use of molar data should give comparable results.
(3) Values in US conventional units (mg/dL) SHOULD NOT be used.
ratio urinary lactate to urinary creatinine =
= (urinary lactate) / (urinary creatinine)
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Neonatal Group
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Ratio for Specimens Collected <= 6 hours After Birth
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normal
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0.09 +/- 0.02
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asphyxia without hypoxic-ischemic encephalopathy
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0.19 +/- 0.12
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asphyxia with hypoxic-ischemic encephalopathy
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16.75 +/- 27.38
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hypoxic-ischemic encephalopathy with favorable neurodevelopmental outcome in 1 year
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0.63 +/- 1.50
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hypoxic-ischemic encephalopathy with adverse neurodevelopmental outcome in 1 year
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25.36 +/- 32.02
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where:
• Favorable neurolodevelopmental outcome at 1 year: normal neurologic development or mild impairment.
• Adverse neurolodevelopmental outcome at 1 year: death, severe cerebral palsy, developmental delay, blindness, deafness.
Interpretation:
• A ratio >= 0.64 for specimens collected <= 6 hours after birth had a sensitivity of 94% and specificity of 100% in identifying infants who developed hypoxic-ischemic encephalopathy.
• Looking at Figure 3, page 333, a rough estimate is that infants with hypoxic-ischemic encephalopathy who have a ratio < 3 tend to have a favorable outcome at 1 year, while those >= 3 tend to have an adverse outcome at 1 year (assuming y axis is LOG10, a horizontal line drawn at 4.5 mm above 1.00 ratio approximates ratio of 3.0)
