Laboratory Medicine Updates - March 17, 2008

University of Virginia Health System

Medical Laboratories

"Quality You Expect, Service You Deserve"

LABORATORY MEDICINE UPDATE

March 17, 2008

New Coagulations Analyzers and Reference Range Changes

The Hemostasis Laboratory implemented new analyzers on March 13th, 2008.  The following reference ranges have been established as a result of this change.

  • Prothrombin Time: 11.8 - 15.3 seconds, ISI = 1.12 and the Geometric mean = 13.5 seconds.
  • Activated Partial Thromboplastin Time (aPTT): 25.3 - 37.4 seconds
  • Fibrinogen: 190-463 mg/dL
  • Thrombin Clot Time: 16-22 seconds
  • Antithrombin (antithrombin III): 83-118%
  • The new unfractionated heparin therapeutic range that corresponds to 0.3 to 0.7 Anti Xa Units/mL has an aPTT range of 57 - 101 seconds.
  • The D-dimer assay used for DIC or part of a thrombophilia panel is ordered as "D-dimer for DIC evaluation" in Carecast and MIS.  The cutoff value for this assay is <305 ng/mL.
  • The D-dimer assay uses methodology that incorporates a High Sensitivity D-dimer for VTE/PE assessment. This test can be ordered as "D-dimer for DVT/PE evaluation" in Carecast and MIS. The cutoff value for this test is < 231 ng/mL and will be accompanied by the following comment:

This assay has been cleared by the FDA for use in conjunction with a clinical pretest probability assessment model to exclude VTE in outpatients suspected of DVT or PE.  At the cutoff value of 230 ng/mL, corresponding to a specificity of about 35%, the negative predictive value is approximately 96% to 100% in a low to moderate risk population and the sensitivity is approximately 93% to 100%.

  • Note that the reporting units for the D-dimer assay have changed from µg FEU/mL to ng/mL.

Any questions should be referred to the Hemostasis Pathology Resident at pic 1663.

 

Reminder: Specimen Collection Requirements

 

The quality and timeliness of patient test results begins with proper collection and labeling of the sample.  This includes specimens drawn for analysis at the Point of Care and for those submitted to Medical Laboratories for analysis.

  • Identify the patient with two patient identifiers prior to collection; name and date of birth are suggested.  This should be an active process - ASK the patient their name and date of birth where possible.  Directly compare the information on the arm-band to the order if the patient is unable to respond.  Do NOT rely on a family member or visitor to identify the patient.
  • Before leaving the room, label the specimen with two patient identifiers, and date and time of collection in front of the patient.  Do NOT pre-label the collection device.
  • Samples collected for Blood Bank and Transfusion Medicine testing must be collected according to the Typenex procedure.  Please contact the Blood Bank at 982-0131 if you need clarification on this procedure.
  • For specimens being submitted to the Medical Laboratories with paperwork, always compare the patient identification on the paperwork for agreement with the information provided on the collection container.

This process is mandated by accrediting agencies and in line with the National Patient Safety Goals.  Your attention to these details is in the best interest of patient safety and care.

 

New Orderable Referral Laboratory Tests

The Serotonin Release Assay for use in the diagnosis of Heparin Induced Thrombocytopenia (HIT) is now orderable electronically.  The analysis performed by the Blood Center of Wisconsin requires knowledge of the type of heparin the patient had received so two different orderable tests have been created: "Serotonin Release Assay Regular Heparin" and "Low Molecular Weight Heparin Serotonin Release Assay".  There is a required data entry field when the order is placed for time of last heparin dose as the performance of the assay is also dependent upon this information.

 

Change to Protein S Antigen Assay Performance

Mayo Medical Laboratories has changed the performance algorithm for the Protein S Antigen assay.  Free Protein S Antigen levels will be measured in all specimens.  The total antigen level will be measured only if the free is abnormal.


Instructions for 24-Hour Urine Collection

 

When providing a patient with a container for a 24-hour urine collection, please provide the following instructions:

  • On the morning the collection is to begin, empty your bladder, but DO NOT collect this urine.
  • Thereafter, for the next 24 hours, ALL urine is to be collected into the large container provided to you. Do not forget to include the first urine obtained on the morning the collection is to end.
  • The container should be refrigerated if possible.
  • Return the container on the same day that the collection is completed to the drop off location provided by the clinic.

 

 

CA 19-9 Testing Now In-House

The Medical Laboratories began testing for CA19-9 (pancreatic/colo-rectal GI tumor marker) in-house on March 13, 2008.  This quantitative immunoassay measures the serum concentration of the CA19-9 tumor associated antigen using the Centaur analyzer.  The two-step sandwich immunoassay using direct chemiluminometric technology uses the monoclonal antibody 1116-NS-19-9 obtained from Fujirebio Diagnostics, Inc. to detect CA19-9 antigen in patient sera.  Assays using other manufacturers' reagents or antibodies may give different results.  The reference interval for this in-house assay is <35 U/mL.  Testing will be performed daily Monday through Friday.

This assay is indicated for the serial measurement of CA19-9 to aid in the management of patients diagnosed with cancers of the exocrine pancreas who presented with increased concentrations of serum CA19-9 at the time of diagnosis.  CA19-9 values must be interpreted in conjunction with all other clinical and laboratory data.   This assay is not indicated for screening or the early detection of pancreatic cancer or as a diagnostic tool to confirm the presence or absence of malignant pancreatic disease.  Patients must possess the ability to express the Lewis blood group antigen or they will be unable to produce the CA19-9 antigen even in the presence of proven malignancy.

Paired analyses of samples with the current send-out test for CA19-9 and the new in-house test is available for patients who are being actively followed for disease management.  Please contact the Chemistry Pathology Resident on-call at pic 1267 to make arrangements.