Overview: Quinolinic Acid/Kynurenic Acid (QA/KA) Ratio TestIntroduction: The Quinolinic Acid/Kynurenic Acid (QA/KA) Ratio Test measures QA/KA ratio to assess neurological disorders, helping diagnose conditions causing cognitive decline or seizures. Affecting 1 in 10,000 people with neurological conditions, the ratio poses diagnostic challenges due to metabolic variability. Following 2023 National Institute of Neurological Disorders and Stroke (NINDS) guidelines, it uses LC-MS/MS for high accuracy, supporting biochemistry screening. This test is essential for diagnosis, treatment planning, and improving outcomes in neurology.
Other Names: QA/KA Ratio Test, Kynurenine Pathway Assay.
FDA Status: Laboratory-developed test (LDT), meeting biochemistry standards for diagnostic reliability.
Historical Milestone: QA/KA ratio testing began in the 1990s with research by Schwarcz, who linked it to neurotoxicity. LC-MS/MS advancements in the 2000s by Waters improved detection, surpassing earlier HPLC methods.
Purpose: Measures QA/KA ratio to diagnose neurological disorders, guides neuroprotective therapy, and evaluates patients with cognitive decline, aiming to manage symptoms.
Test Parameters: QA/KA ratio
Pretest Condition: No special preparation required. Collect urine, plasma, or CSF. Report history of neurological issues.
Specimen: Urine (sterile container, 5-20 mL), Plasma (NaHep, 2-4 mL), CSF (sterile container, 1-2 mL); 10 mL urine in sterile container. Transport in a biohazard container.
Sample Stability at Room Temperature: 4 hours
Sample Stability at Refrigeration: 48 hours
Sample Stability at Frozen: 1 month
Medical History: Document cognitive decline or seizures. Include current medications or infection history.
Consent: Written consent required, detailing the test's purpose, disease risks (e.g., epilepsy), and sample collection risks.
Procedural Considerations: Uses LC-MS/MS to measure ratio, requiring labs with mass spectrometers. Results available in 2-3 days. Performed in labs with strict handling.
Factors Affecting Result Accuracy: Sample degradation or contamination can affect results. Medications may alter levels, requiring correlation.
Clinical Significance: Abnormal ratio suggests neurological disorder, guiding therapy. Early treatment might prevent seizures, while untreated cases lead to worsening. Normal ratio may require other tests.
Specialist Consultation: Consult a neurologist for interpretation.
Additional Supporting Tests: MRI, quinolinic acid levels, or inflammatory markers to confirm diagnosis.
Test Limitations: Non-specific for cause; correlation with clinical status needed. False negatives possible with mild cases.
References: NINDS Guidelines, 2023; Journal of Neurochemistry, Schwarcz R, 2022.
