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Laboratory Medicine

Test Directory / Folate


Brown clotted serum, gel barrier

Common AbbreviationsFOL
Tube typeBrown clotted serum, gel barrier
Clinical IndicationUsed in the investigation of suspected folate deficiency. Low folate intake, malabsorption as a result of gastrointestinal diseases, chronic alcoholism, pregnancy and drugs such as phenytoin are causes of folate deficiency. Folate and B12 deficiency impair DNA synthesis, causing macrocytic anaemias.
Specimen TypeBlood
Sample typeSerum
Minimum Volume0.5mL If requesting more than 10 tests please send an additional brown clotted serum sample.
Special PrecautionsFasting sample preferred.
Stability48 hours at 20 - 25°C, 72 hours at 2 - 8°C and 28 days at -20°C.
Turnaround TimeInpatient: 24 hours Outpatient/ GP: 24 hours
LaboratoryYork and Scarborough
Reference Interval3.89 - 26.8µg/L (Quoted by the manufacturer)
LimitationsAnalysis should not be performed on icteric or lipaemic samples. Haemolysis may significantly increase folate values due to high concentrations of folate in red blood cells. Therefore, haemolysed samples are not suitable for analysis. The assay is unaffected by biotin < 86.1 nmol/L or < 21 ng/mL. No interference was observed from rheumatoid factors up to a concentration of 1000 IU/mL. No interference was observed from IgG < 1.6 g/dL; IgA < 0.4 g/dL; IgM < 1.0 g/dL Samples should not be taken from patients receiving therapy with high biotin doses (i.e. > 5 mg/day) until at least 8 hours following the last biotin administration. In vitro tests were performed on 16 commonly used pharmaceuticals. No interference with the assay was found. Samples with extremely high total protein concentrations are not suitable for use in this assay, since they may lead to the formation of protein gel in the assay cup. In rare cases, high titres of antibodies to analyte specific antibodies, streptavidin or ruthenium can occur. It is contraindicated to measure samples of patients receiving therapy with certain pharmaceuticals, e.g. methotrexate or leucovorin, because of the cross-reactivity of folate binding protein with these compounds.
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