Laboratory Medicine Updates - May 23, 2008

University of Virginia Health System

Medical Laboratories

"Quality You Expect, Service You Deserve"

LABORATORY MEDICINE UPDATE

May 23, 2008

In this issue:

Joint Commission Compliance Issue

Fractionated Alkaline Phosphatase Interpretive Comment

Correct Procedure for Sending Blood Gas Syringes to the Core Lab

Vasculitis Panel

Epstein-Barr Virus Testing

Antibodies to Extractable Nuclear Antigens

Glomerular Basement Membrane (GBM)

Coding Update for HIV Testing

Update on Transfusing Cryoprecipitate

 

Joint Commission Compliance Issue

In order to comply with a Joint Commission standard regarding laboratory testing, all charts have been updated with a document that states:

For all laboratory reference ranges and units of measure, refer to the electronic medical record on date of service.

 In the blue charts, this document can be found directly behind the NPSG laminated sheet.  In the door side charts it is a statement on the first page of the Quick Care Tips document.  If you find a chart that is missing this information, please contact Jennifer De Arment at 3-4752 or Denise Eavers at 4-8507.

 

Fractionated Alkaline Phosphatase Interpretive Comment

In order to assist in the interpretation of fractionated alkaline phosphatase test results, the following comment will be appended to all results beginning approximately June 1, 2008:

"Bone alkaline phosphatase (AP) is very heat sensitive (bone burns best), placental AP is very heat stable, while liver AP (and several other APs) are intermediate.  The report shows the total AP, the residual AP activity after heating the serum (15 min at 56 degrees), and the percent of initial AP remaining after heating.   In distinguishing between liver and bone origins of AP, residual activities greater than 35% are consistent with liver disease (as well as with pregnancy and some other disorders, including certain tumors) while activities less than 23% suggest bone disease."

 

Correct Procedure for Sending Blood Gas Syringes to Core Lab

Please remember that the correct procedure for sending blood gas syringes to the Core Laboratory includes:

  • Remove the needle from the syringe and replace with Syringe Luer Lock Top
  • Place the labeled specimen in a clear Ziploc bag with the paperwork in the pocket.
  • Place the Ziploc bag in a plastic bag that contains ice. DO NOT PLACE SPECIMEN DIRECTLY ON ICE.
  • Completely close all bags and place in a large Ziploc prior to sending through the Tube System.

 

Vasculitis Panel

The methodology and result reporting for neutrophil cytoplasmic antibody (ANCA) has changed.  The Bio-Rad Bioplex instrument uses specific MPO and PR3 proteins and is reported in semi-quantitative units of antibody index (AI).  This replaces the indirect immunofluorescence method as well as the qualitative results and pattern identification.  Additionally, the turn-around-time will be improved as the assay will be performed more frequently than once per week.  Antibodies to MPO correlate with a perinuclear pattern while antibodies to PR3 correlate with a cytoplasmic pattern.  By ordering a vasculitis panel you will get both MPO and PR3 results. 

Reference Interval:

Negative           <1.0 AI

 

Epstein-Barr Virus Testing

The Medical Laboratory will offer all EBV testing in-house as of June 1, 2008.  There are two panels available for clinicians to use to screen, diagnose and monitor patients.  The EBV Profile replaces the current acute panel currently sent to a referral laboratory, so turn-around-time will be reduced.  Results are reported in semi-quantitative units of antibody index (AI). 

Result Interpretation:

Negative           <0.9 AI

Equivocal         0.9 to 1.0 AI

Positive            >1.0 AI

 

EBV Immune Status:  this panel tests for antibodies to the Epstein-Barr virus nuclear antigen (EBNA-IgG) and viral capsid antigen (VCA-IgG)

EBV Profile:  this panel tests for antibodies to EBNA-IgG, VCA-IgG, VCA-IgM, early antigen (diffuse) IgG and heterophile antibodies IgM

 


 

Antibodies to Extractable Nuclear Antigens

The methodology and result reporting for antibodies to Extractable Nuclear Antigens (ENA) have changed.  The Bio-Rad Bioplex instrument uses a combination of native, purified and recombinant antigens, and the results are reported as semi-quantitative units of antibody index (AI).  This replaces the qualitative double diffusion method.  While these tests may be ordered separately, there are two established panels available.

Reference Interval:

Negative           <1.0 AI

ENA Mini Profile:  SS-A, Sm, RNP

ENA Full Profile:       SS-A, SS-B, Sm, RNP, SM/RNP, SCL70, Jo-1, Centromere B, Chromatin, Ribosomal P

 

Glomerular Basement Membrane (GBM)

The methodology and reporting units of glomerular basement membrane antibodies has changed.  The new assay (Bio-Rad Bioplex) uses the same antigen as the previous EIA (bovine purified alpha 3(IV) protein).  With the more automated platform, the turn-around-time will be reduced as testing will be performed more frequently.  Results will continue to be reported in semi-quantitative units with a new cutoff value.

Reference Interval:

Negative           <1.0 AI

 

Coding Update for HIV Testing

In September 2006, the Centers for Disease Control and Prevention (CDC) issued recommendations for HIV in health care settings.1  The recommendations encourage HIV testing as a routine part of medical care.  In April 2008, the American Medical Association and the American Academy of HIV Medicine published ICD-9 coding guidelines for such testing.  These guidelines are summarized in the table below:

Situation

Code

Description

Patient seen as part of routine medical exam

V70.0

Routine general medical examination at a health care facility

Patient seen to determine his/her HIV status (can be used in addition to routine medical exam)

V73.89

Special screening for other specified viral diseases

Asymptomatic patient in a known high-risk group for HIV (can be used in addition to routine medical exam)

V69.8

Other problems related to lifestyle

Counseling provided during the encounter for the test (add additional code if applicable)

V65.44

HIV counseling

When the patient returns for the test results:

Situation

Code

Description

Returning patient informed of his/her HIV negative test results

V65.44

HIV counseling

Returning patient informed of his/her HIV positive test results AND patient is asymptomatic

V08

Asymptomatic HIV infection status

Returning patient informed of his/her HIV positive test results AND patient is symptomatic

042

HIV disease

HIV counseling provided to patient with positive test results

V65.44

HIV counseling

1 "The Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Setting."  Morbidity and Mortality Weekly Report.  September 22, 2006 (55:RR-14).

 

Update on Transfusing Cryoprecipitate

Preparing Cryoprecipitate

Cryoprecipitate (cryoprecipitated antihemophilic factor) is prepared by isolating precipitated, high molecular weight glycoproteins from a unit (bag) of fresh frozen plasma (FFP).  A bag of cryoprecipitate is created by thawing a bag of FFP at 1-6 oC.  The thawed FFP bag is then centrifuged, the plasma is expressed to create cryopoor plasma and cryoprecipitate remains in the original bag.  Ten to 15 mL of the plasma are left behind to resuspend the cryoprecipitate.  After completing this process, the cryoprecipitate bag is frozen to < -18 oC for a 12 month shelf life.  The proteins of cryoprecipitate include fibrinogen (factor I), fibronectin, factor VIII, factor XIII and von Willebrand factor (vWF).  For transfusion, each cryoprecipitate bag is thawed at 30 to  37 oC and pooled. 

Current Cryoprecipitate Indications

  • Fibrinogen replacement caused by loss due to DIC, bleeding, etc.
  • Dysfibrinogenemia, congenital or acquired.
  • Factor XIII deficiency
  • Uremic platelet dysfunction and bleeding.  Cryoprecipitate is a second choice therapy following desmopressin (DDAVP).
  • Historically used for:
    • Hemophilia A before factor concentrates were available for Factor VIII replacement (e.g., Kogenate, Helixate, Recombinate, and Refacto)
    • von Willebrand syndromes before factor concentrates were available (e.g., Alphanate and Humate P)
    • Fibrin sealant before FDA approved fibrin sealants (e.g., Tisseel and Evicel)

 

Cryoprecipitate Contraindications

  • Cryoprecipitate is NOT indicated for warfarin reversal or bleeding in a vitamin K deficient patient because it does not contain clinically significant amounts of factors other than fibronectin, vWF, fibrinogen, factor VIII and factor XIII.  Cryoprecipitate should not be considered a "concentrated" form of FFP.

Cryoprecipitate Dosing

1) The typical dose is 1 bag of cryoprecipitate per 10 kg of body weight. This is a quick and easy way to estimate an appropriate dose of cryoprecipitate.

a) 70 kg man x 1 bag/10 kg body weight = 7 bags of cryoprecipitate

2) The following calculation allows determination of a specific cryoprecipitate dose to attain a predetermined fibrinogen level:

a) Calculate Blood Volume = Body weight x 70 mL/Kg

i) e.g., 70 kg x 70 mL/kg = 4900mL

b) Calculate Plasma Volume (PV) = Blood Volume x (1 - Hematocrit)

i) e.g., 4900 mL x [1- 0.40] = 2940 mL

c) Calculate mg fibrinogen needed = Plasma volume x desired change in fibrinogen concentration

i) Subtract desired level from current level

(1) e.g., 150 mg/dL - 100 mg/dL = 50 mg/dL

ii) Divide the answer by 100 to convert dL to mL

(1) e.g., 50 mg/dL x 1 dL/100mL

iii) Multiply level change by PV

(1) e.g., 0.5 mg/mL x 2940 mL = 1470 mg

d) Calculate bags of cryoprecipitate needed = Fibrinogen needed / 150 mg per bag of cryoprecipitate

i) e.g., 1470 mg x 1 bag Cryoprecipitate/150 mg = 9.8 ->10 bags of cryoprecipitate

e)      Summary Formula

(Post Fib-Pre Fib) x

(PV)  x

(1 dL)

x

(1 bag cryo)

=# Bags of Cryoprecipitate

(100 mL)

(150 mg Fib)

As always, blood bank and transfusion medicine personnel are available 24 hours a day at 4-2273 (4-CARE) to assist with any questions or concerns you may have regarding cryoprecipitate and other blood products.