DNPH Test Dinitro Phenyl hydralazine

Blood

Report in 72Hrs

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No Fasting Required

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Rare biochemical test (for hydralazine reaction).

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DNPH Test (Dinitrophenylhydrazine) - Comprehensive Medical Information Guide

Section 1: Why is it done?
- Test Purpose: The DNPH test is a urine screening test designed to detect organic acids in the urine, particularly those associated with metabolic disorders affecting the breakdown of amino acids and organic compounds.
- Primary Indications: Screening for organic acidurias and other metabolic disorders in newborns and infants; detecting branched-chain amino acid metabolism disorders; identifying medium-chain acyl-CoA dehydrogenase deficiency (MCADD) and similar fatty acid oxidation disorders.
- Clinical Scenarios: Performed during newborn screening programs; when infants present with developmental delay, failure to thrive, or metabolic acidosis; during investigation of recurrent hypoglycemia; when family history suggests inherited metabolic disease; during evaluation of unexplained neurological symptoms in children.
Section 2: Normal Range
- Normal Result: Negative or No Color Change - Indicates absence of organic acids in urine; represents normal metabolic function with proper processing of amino acids and fatty acids.
- Reference Range: Organic acids in urine: <5 mmol/mol creatinine; Normal values vary slightly by age, with lower ranges for infants and newborns.
- Abnormal Results: Positive result (Color change - typically yellow, brown, or purple depending on specific acids present): Indicates presence of organic acids suggesting metabolic disorder; Mild positivity may require confirmation; Strong positivity suggests significant metabolic dysfunction.
- Units of Measurement: Qualitative (Positive/Negative) or semi-quantitative grading (1+ to 4+); May be reported as mmol/mol creatinine when quantified.
Section 3: Interpretation
- Negative Result Interpretation: Normal metabolic function; No evidence of organic acidurias; Amino acid and fatty acid metabolism proceeding normally; Low risk for major metabolic disorders detected by this screen.
- Positive Result Interpretation: Indicates elevated organic acids in urine suggesting metabolic disorder; Requires confirmation with additional testing (gas chromatography-mass spectrometry, plasma amino acid analysis); Severity correlates with intensity of color change.
- Specific Organic Acid Patterns: Different organic acids produce different color reactions with DNPH; Branched-chain ketoaciduria produces characteristic color pattern; Methylmalonic acidemia shows specific organic acid profile; Medium-chain acyl-CoA dehydrogenase deficiency produces distinctive metabolites.
- Factors Affecting Results: Timing of specimen collection (critical in acute metabolic episodes); Hydration status and urine concentration; Dietary protein intake at time of testing; Illness or metabolic stress may elevate organic acids; Medications that affect metabolic pathways; Age-related variations in normal ranges.
- Clinical Significance: A positive DNPH test is significant for early detection of serious metabolic disorders that can lead to neurological damage if untreated; Early intervention based on positive results can prevent developmental complications; False negatives can occur in some metabolic disorders, so clinical correlation is essential; Serial testing may be needed during metabolic crises.
Section 4: Associated Organs
- Primary Organ Systems Involved: Liver (primary site of amino acid and fatty acid metabolism); Kidneys (filtering and elimination of organic acids); Mitochondria (site of fatty acid oxidation and amino acid catabolism); Brain (most vulnerable to metabolic dysfunction); Pancreas (in disorders affecting glucose metabolism).
- Associated Metabolic Disorders: Maple Syrup Urine Disease (MSUD) - branched-chain amino acid disorder; Methylmalonic Acidemia - affecting vitamin B12 metabolism; Propionic Acidemia - propionyl-CoA carboxylase deficiency; Isovaleric Acidemia - leucine metabolism disorder; Medium-Chain Acyl-CoA Dehydrogenase Deficiency (MCADD); Glutaric Acidemia Type I and II.
- Common Clinical Presentations: Developmental delay and intellectual disability; Recurrent hypoglycemia and hypoketotic hypoglycemia; Metabolic acidosis; Failure to thrive and poor feeding; Seizures and neurological manifestations; Lethargy and developmental regression; Characteristic odor (maple syrup, cat-like, or sweaty feet smell); Cardiomyopathy in some disorders.
- Potential Complications: Irreversible neurological damage if diagnosis delayed; Acute metabolic crisis with coma risk; Sudden infant death from acute decompensation; Progressive neurological deterioration; Movement disorders and dystonia; Auditory impairment; Developmental regression; Chronic kidney disease in some conditions.
Section 5: Follow-up Tests
- Confirmatory Testing: Gas Chromatography-Mass Spectrometry (GC-MS) of urine - gold standard for identifying specific organic acids; Plasma amino acid analysis - identifies elevated branched-chain amino acids and other metabolic markers; Plasma acylcarnitine profile - evaluates fatty acid oxidation disorders; Plasma carnitine levels.
- Additional Diagnostic Tests: Blood glucose measurement - assess for hypoglycemia; Arterial or venous blood gas - evaluate metabolic acidosis; Ammonia levels - check for hyperammonemia; Lactate and pyruvate - assess lactic acidosis; Liver function tests (AST, ALT, bilirubin); Renal function (creatinine, BUN); Coagulation studies in severe cases.
- Genetic Testing: DNA sequencing of relevant genes (BCKDHA, BCKDHB for MSUD; MUT, MMAA, MMAB for methylmalonic acidemia; ACAD9 for MCADD; PCC for propionic acidemia); Carrier testing for family members; Prenatal genetic counseling for affected families.
- Neurological and Imaging Studies: Brain MRI - assess for leukodystrophy, basal ganglia involvement, or structural abnormalities; EEG - evaluate for seizure activity; Developmental assessment and neuropsychological testing; Auditory brainstem response (hearing assessment); Cardiac echo (for cardiomyopathy screening).
- Monitoring Frequency: For confirmed metabolic disorders: plasma amino acids and acylcarnitines monthly to quarterly; Urine organic acids 1-2 times yearly during stable periods; More frequent testing during acute illness or metabolic crisis; Liver and kidney function tests every 6-12 months; Neurological evaluation annually; Audiological testing annually.
- Related Complementary Tests: Newborn screening tandem mass spectrometry (expanded screening panel); Urine ketones (may be elevated); Urine pH (assessment of acidification); Dietary assessment and nutritional markers; Vitamin B12 and folate levels (if methylmalonic acidemia suspected).
Section 6: Fasting Required?
- Fasting Requirement: No - Fasting is NOT required for the DNPH test. This is a urine screening test performed on a random urine specimen.
- Specimen Collection: Random urine specimen can be collected at any time of day; Morning first-void urine preferred due to higher concentration; For newborns, specimens collected from diaper during routine care; No special collection technique required; 5-10 mL of urine sufficient for testing.
- Special Instructions: Specimen should be refrigerated or sent to lab promptly; If acute metabolic crisis suspected, test during symptomatic period for optimal detection; Inform laboratory of any recent fever, illness, or medication changes; Document time of specimen collection; For newborn screening, timing relative to feeding may influence results.
- Medications to Avoid: No medications need to be withheld specifically for this test; However, inform laboratory if patient is on: Antibiotics (may affect gut flora and organic acid production); Vitamins or supplements (particularly B vitamins and L-carnitine supplements); Anti-seizure medications; Any medications affecting amino acid metabolism.
- Patient Preparation: Normal diet and hydration maintained; No dietary restrictions required; Continue regular feeding schedules for newborns; Adequate hydration important (concentrated urine provides better results); Normal activity and routine acceptable; Notify provider of acute illness, fever, or metabolic symptoms occurring around test time.

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