DRVV Confirm Normalized Ratio; SCT Confirm Normalized Ratio, if indicated: SCT Mix, DRVVT Mix

3 to 5 days

Monday through Friday, batched, run 1 to 2 times per week.

Three full 2.7 mL LIGHT BLUE top tubes, 3.2% sodium citrate. Hemostasis & Thrombosis Lab sodium citrate specimens must be processed and frozen within 2 hours of specimen collection. Stability is 14 days at -70 C.

Draw volume is critical due to the liquid anticoagulant. Allow tubes to fill by vacuum.
• Tubes with rubber stopper: fill to line on label.
• Tubes with plastic (Hemogard) cap: the fill level is above the top of the label.
• Syringe: do not remove the vacutainer stopper. Insert the needle through the stopper and allow the tube to fill by vacuum. Do not overfill the vacutainer.
• Pediatric tubes have no vacuum. Remove the cap and add blood to the 1.3 mL mark. Do not overfill.

OHSU clinics must cab specimen to the H&T Lab, Dillehunt Hall, Room 3050 if processing is delayed or not possible on site. A phone call is helpful to alert the lab at 503-494-8445.

Detailed specimen collection and processing instructions are located under Lab Sections and then the Hemostasis and Thrombosis (Opens in a new window) section.

For referral testing, submit four tubes, each with 1.0 mL frozen platelet poor citrated plasma.

Three full pediatric 1.3 mL LIGHT BLUE top tubes, 3.2% sodium citrate. Hemostasis & Thrombosis Lab sodium citrate specimens must be processed and frozen within 2 hours of specimen collection. Stability is 14 days at -70 C.

For pediatric patients requiring multiple coagulation tests, please call 503-494-7383 regarding draw volumes.

dRVVConfirm Normalized Ratio: less than or equal to 1.20
SCT Confirm Normalized Ratio: less than or equal to 1.16

• To exclude anticoagulant effects, a reflex Heparin, Thrombin Time, and INR will be performed when the lupus panel screens or normalized ratios are prolonged.
• 50/50 mix will be performed if SCT screen or dRVVT screen is prolonged.

In an effort to comply with the Clinical and Laboratory Standards Institute (CLSI) guidelines for Laboratory Testing for the Lupus Anticoagulant while also following the manufacturers recommendations for each test within the lupus panel, the dilute Russels viper venom (dRVV) and SCT arms of lupus testing will be reported as a total ratio.

Testing for lupus inhibitors is not recommended while a patient is on anticoagulation therapy because heparins, direct Xa inhibitors, warfarin, and direct thrombin inhibitors variably confound the parent test systems (SCT, dRVVT, and mixing studies). To mitigate the effects of standard heparin within the assay, an agent is added to the test system which may abate standard heparin at concentrations up to 1.0 U/mL, but does not mitigate against effects of other anticoagulants, including low molecular weight heparins. Coumadin may elevate the dRVVS ratio due to its effect on Factors II and X, but the DVV confirm ratio (dRVVC) may be normal in this situation. An elevated dRVVS ratio with an abnormal dRVVC ratio is suggestive of a lupus inhibitor, however warfarin effects cannot be entirely excluded. Direct Xa inhibitors, such as rivaroxaban and apixaban, will variably affect PTT and PT mixing studies often leading to spurious results, most commonly appearing as an incomplete correction of the mix, among other interferences.

Repeat testing of initial abnormal studies is recommended after at least 12 weeks, since transient LAs (often associated with infection or medication effect) are common and may not have the same clinical implications or require the same treatment as chronic LAs of extended duration. The Lupus Inhibitor panel does not include serologic studies (anti-cardiolipin and anti-beta 2 glycoprotein 1) which are also useful in evaluating anti-phospholipid syndrome (APS). For comprehensive APS evaluation follow ISTH guidelines.

Methodology of SCT and dRVVT: clotting assay.

Dilute Viper Venom Time (DVVT) with Reflex to DVV Confirm Ratio
Lupus Anticoagulant
Lupus Panel