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Lab Manual for Moffitt-Long and Mount Zion

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Modified Inhibitor Titer

Item Value
Available Stat? No
Test code MODIT
Test group Factor Inhibitor titer
Performed by Parnassus Hematology
In House Availability Monday-Friday 0800-1400
Method Clotting assay(STAGO)
Patient Preparation Deliver samples to Hematology for processing. Freeze platelet poor plasma at -20C
Collection Instructions 1. Check the expiration date on the label of the blue top vacutainer before drawing the patient

2. For blood collection in a sodium citrate blue top, the tube must be filled to above the Minimum Fill Indicator on the tube. It is crucial to wait and allow the tube to stop filling before removing it from the needle.

3. With use of a butterfly needle, draw about 1 cc using a separate blue top to remove air from tubing, discard the first tube and then draw a second blue top tube filled to the full extent of the vacuum.

4. Tubes should not be filled past the Maximum Fill dashed line by either using a syringe or removing the tube cap.

For patients with Hct's ≥ 55% please contact Hematology (415-353-1747) to obtain blue top tubes with adjusted citrate volumes in order to maintain the proper citrate to plasma ratio for coagulation studies.
Container type 2.7 mL Blue top filled to full extent of vacuum x 2
Amount to Collect 5.4 mL blood
Sample type Citrated plasma
Preferred volume 2 mL plasma
Min. Volume 1 mL plasma
UCSF Rejection Criteria Samples collected in outdated blue top vacutainer. Over-filled or under-filled tubes may be rejected
Units Bethesda Units (BU)
Normal range < 0.25 BU
Synonyms FVIII titer; Factor 8 specific mini titer
Stability 4 hours
Turn around times 1-5 days
Additional information Known factor VIII deficient patients may develop antibodies to transfused factor, and thereby develop inhibitors. When there is a clinical indication to screen for inhibitors in factor deficient patients or there is clinical suspicion for inhibitor development, a modified inhibitor titer may be performed rather than a factor inhibitor screen (mixing study). The modified inhibitor titer can detect inhibitors as low as 0.25 Bethesda Units (BU).

Because the modified inhibitor titer has a 2 hour incubation step, slow acting inhibitors may be detected. An in house UCSF study in the Fallof 2008 indicated that the modified inhibitor titer can detect low titer inhibitors missed by the factor inhibitor screen. This study also showed that the modified inhibitor screen can yield a result of <0.25 BU in patients for whom the factor inhibitor screen gave an equivocal result.

If a Factor VIII level has not been performed within the preceding 24 hours one will be automatically ordered and charged for before the inhibitor titer is performed.

If unusual findings are noted a pathologist review and interpretation may be performed and separately billed for
LOINC code 3206-0
LDT or Mod FDA? Yes
Last Updated 4/1/2014 11:37:20 AM
Entry Number 1260

If you have additional questions regarding this test, please call: 415-353-1667

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