74 Laboratory: Methods, Standards and Cost Effective Testing (Part 2)

Donna Castellone MS, MT(ASCP)SH

2011 Annual Meeting – Las Vegas, NV

AMERICAN SOCIETY FOR CLINICAL PATHOLOGY 33 W. Monroe, Ste. 1600 Chicago, IL 60603

74 Coagulation Laboratory: Methods, Standards and Cost Effective Testing (Part 2)

This session features a case study approach to examine issues that impact coagulation results: sources of errors, methods of standardization, and new and cost effective testing. is complex and there can be a disconnect in what the clinician expects to come forth from the laboratory and what can actually be provided by the laboratory.

• Identify solutions to areas of coagulation testing that can be enhanced by implementing good laboratory practices and standard operating procedures. • Analyze real case studies and how to troubleshoot testing to determine the root cause and what steps to take to prevent reoccurance. • Enhance general knowledge of coagulation, standards and methods.

FACULTY:

Donna Castellone MS, MT(ASCP)SH

Entire Pathology Team Hematopathology Hematopathology 1.0 CME/CMLE Credit

Accreditation Statement: The American Society for Clinical Pathology (ASCP) is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education (CME) for physicians. This activity has been planned and implemented in accordance with the Essential Areas and Policies of the Accreditation Council for Continuing Medical Education (ACCME).

Credit Designation: The ASCP designates this enduring material for a maximum of 1 AMA PRA Category 1 Credits™. Physicians should only claim credit commensurate with the extent of their participation in the activity. ASCP continuing education activities are accepted by California, Florida, and many other states for relicensure of clinical laboratory personnel. ASCP designates these activities for the indicated number of Continuing Medical Laboratory Education (CMLE) credit hours. ASCP CMLE credit hours are acceptable to meet the continuing education requirements for the ASCP Board of Registry Certification Maintenance Program. All ASCP CMLE programs are conducted at intermediate to advanced levels of learning. Continuing medical education (CME) activities offered by ASCP are acceptable for the American Board of Pathology’s Maintenance of Certification Program. 10/8/2011

Part II:

Coagulation Laboratory: Methods, Standards & Cost Effective Testing

Donna D. Castellone

Understanding Coagulation

• Case Studies

- clinical picture - analysis - diagnosis

Case Study • A 15 yr old female presents with heavy periods • Her HGB is 9.0 g/dl • She has had intermittent periods of nose bleeding as a child • An evaluation for a bleeding work-up was ordered • PT= 12.1 sec • APTT= 42.1 sec • Mixing study: APTT 1:1 mix = 31.5 sec Correction • FVIII= 38%

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Additional Testing:

• Decreased Factor VIII, need to distinguish between vWD and Hemophilia • vWD is autosomal dominant, 1/200 people, most common cause of bleeding • This is a test of - ppyrimary hemostasis • Hemophilia is sex-linked recessive • Mostly in males- secondary hemostasis

Hemophilia or vWD

• Second level testing: • Ristocetin cofactor: 38% (nr 50-150%) • vWF: antigen: 35% (nr 50- 150%)

• Diagnosis: von Willebrand Disease

• Multimer analysis: all multimers decreased

• Type 1 VWD

Von Willebrand Disease

• Described in 1926 by Eric von Willebrand described a bleeding disorder that occurred in 24/66 families

• vW factor is a plasma protein that mediates the initial adhesion of platelets at the site of vascular injury

• It also stabilizes FVIII in circulation

• Caused by a deficiency or dysfunction of vWF

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von Willebrand Disease:

• Affects 1-2% of general population, about 2.6 million people

• Autosomal dominant: 50% chance of passing the gene to a child

• Caused by a deficiency and/or qualitative abnormality of the VWF protein

• Can be acquired with certain malignancies, drugs or autoimmune disorders

Von Willebrand Factor • vWF is a multimeric high molecular weight protein present in plasma and platelets • In response to vascular injury it mediates adhesion to the subendothelium and platelet aggregation • Serves as a carrier protein and a stabilizer for FVIII- which is why FVIII i s d ecreased i n VWD • Synthesized in endothelial cells and megakarocytes controlled by a gene on chromosome 7 • Stored in the Weibel-Palade bodies

Types of von Willebrand Disease:

• Type 1: decreased vWF activity & antigen 70-80% of cases; mild bleeding symptoms, may be asymptomatic.

• Type 2: abnormal vWF protein, qualitative, 2:1 ratio of activity to antigen; deficiency of higher weight multimers; mild to severe bleeding

• Type 3: severely reduced or absent circulating vWF, rare & life threatening bleeding

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Clinical Findings • Mucosal bleeding (epistaxis, gingival bleeding. menorrhagia)

• Superficial ecchymosis: common

• Hemarthrosis, delayed bleeding, deep dissecting hematoma: rare

• Not one laboratory test can make the diagnosis

• Some screening tests may be normal, need specific vW laboratory tests.

How to test:

• PT, APTT, , PLT • FVIII measures the ability of vWF to bind and maintain the level of FVIII in circulation • vWF Antigen measures the concentration of vWF protein in plasma • vWF Ristocetin cofactor assay: functional assay of vWF measures its ability to interact with normal platelets • the antibiotic ristocetin causes vWF to bind to platelets, resulting in clumps and remove from circulation

Additional testing:

• Collagen binding assay: ELISA assay

• Ristocetin Induced Platelet Aggregation (RIPA)

• vWF multimers: looks at the different molecular forms of vWF from dimer to high molecular weight multimers (HMWM). This is important in determining subtypes of vWD

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Blood Typing: • Different blood types have different normal ranges of vWF • May be a consideration when classifying patients:

Type O = 36-157%

Type A = 49-234%

Type B = 57-241%

Type AB= 64-238% Technical Manual 9th ed AABB

NHLB/NIH Guidelines TypeDescription R; vWF Ag FVIII R:CoF/A CoF %% % g NL 50-20050-200 NL >.5-.7 1 Partial quantitative vWF deficiency <30 <30 NL or >.5-.7 low 2A Decreased vWF dependent plt <30 <30- NL or <.5-.7 adhesion 200 low & selective deficiency of HMWM 2B Increased vWF affinity to GPib <30 <30- NL or <.5-.7 200 low 2M Decreased vWF dependent platelet <30 <30- NL or <.5-.7 adhesion 200 low 2N Markedly decreased vWF binding 30-20030-200 Very >.5-.7 affinity for FVIII low 3 Complete deficiency of vWF <3 <3 Very NA low

Von Willebrand testing

• Sample integrity is important, antigen is more stable than activity • Should freeze sample ASAP, but after thawing do not place on ice • Thaw in water bath • Mix, mix and mix • Blood type is important

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Case Study:

• A pregnant women has a routine OB visit

• This is her third pregnancy, no prior problems

• Upon taking a history, her only complaint is shortness of breath

• The physician orders a work-up

Thrombosis & Pregnancy:

• 6 times more thrombotic • Recurrent rate: 1/71 • Most prone 3rd trimester • Post-partum • Can have micro vascular thrombosis • 110 women with obstetrical complaints- 53 had thrombophilia-50% • PE most common cause

Recommended Thrombosis ‘Panel’ • APC Resistance screen • Protein C activity • Protein S activity • Antithrombin activity • Prothrombin 20210 gene mutation • Factor VIII • Lupus screening • Homocysteine

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c2 Laboratory Evaluation ¾ Must perform a panel of tests ¾ No global test available

¾ Must confirm plasma based assays before establishing diagnosis

¾ Many drugs and physiologic conditions may influence results

¾ Should consider evaluation of family

What happens? • Increase in VII, VIII, IX, X and fibrinogen

•vWF

• Increased venous stasis

• Increased activation of platelets

• Increased PAI-1

• Physiological resistance to APC

Why?

• Hemostatic changes:

– Physiological changes

– Congenital: Thrombophilia

– Mechanical: Change in Uterus

– 1600 women/day die in pregnancy

7 Slide 19 c2 castdo10, 12/17/2010 10/8/2011

Additional risks:

• DVT 35 fold increased risk: 5/100 • 50% of women that have thrombotic • Post partum ovarian DVT 1:500-1:2000 women • High risk in thrombophilia patients – 30-36% ATIII deficiency – 3-10% Protein C deficiency – 0-6% Protein S deficiency pre-partum – 0-15% post-partum – 46% APCR

Acquired Risk Factors:

• Cesarean delivery

• Maternal age>35 = 3 X risk; >40 =6 X risk

• Obesity >180 lbs

• Surgical procedure during pregnancy or post partum

How do you treat?

• can cross the placenta, risk to the fetus

• Can use 13-30 weeks, or post partum

• doesn’ t cross placenta, monitor with APTT

• Aspirin

• LMWH safe, 1/day, must remove 24 hours before labor

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Advantages:

• Excessive blood loss is >600mls

• APCR + patients have a lower risk

• 14% of APCR – patients will bleed

• Only 1% of APCR + patients bleed

Results:

• Fibrinogen= 485mg/dl (180-400) • Factor VIII=210% (50-150%) • Factor V Leiden: negative • : negative • AT= 82% (80-120%) • Protein C = 84% (70-130% • Protein S= 50% (62-154%)

• What do we see?

Diagnosis:

• Physician tells the patient she was Protein S deficient

• Recommends a therapeutic abortion

• After much thought the patient agreed, since she had 2 small children at home

• What is wrong with this picture

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Protein S:

• Protein S is a Vitamin K dependent factor

• It is an inherited disorder, occurring in about 3% of the thrombotic population

• However, protein S is normally decreased in pregnancy

• It also is decreased during the first few days of a women’s cycle

How to test:

• This is a case where an abnormal result is normal

• Information is vital

• Not knowing can have consequences

Case Study

• A pediatric samples from a 3 month old sent to laboratory for testing • Lupus work-up • Pediatric samples: small volume, different ranges • Transient? True LA? Many issues

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Results

• PT= 16.1 APTT=54.7 • 1:1 mix = 15.9 & 52.1 • Continue LAC work-up • Drvvt screen= 114. 0 sec (abn) • Drvvt confirm= 128.0 ratio= 0.9; neg • Hexagonal phase= positive (strongly 21.9 sec) • Lupus, right?

Result Review

• Principle of DRVVT, is screen uses low concentration of ppl, prolongs result • Confirm uses high concentration result should shorten • Very prolonged results, confirm is longer than screen • Different than APTT - suspicious.....

Factor Assays also performed

Factor 1:10 1:20 1:40

VIII 45% 65% 90%

IX 32% 46% 62%

XI 50% 71% 94%

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Additional information

• Looked like an inhibitor, was heparin on board • time = 14.1 sec PNP=13.8 sec normal • Running out of sample • Techs were running out of patience

Additional Information

• HIT testing • Positive for HIT • Patient not on Heparin • Patient was on Argatroban

Baby had HIT, put on a DTI, laboratory not notified, caused abnormal results

Not just heparin and coumadin anymore: • Large compendium of anticoagulation • Newest are anti-thrombin's • These direct inhibitors against IIa • Cannot be monitored by an APTT, or a

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Direct Thrombin Inhibitors (DTI's)

1. Directly bind to and inhibit thrombin’s interaction with its substrate 2. Action not mediated through antithrombin 3. Do not interact with other plasma proteins 4. Do not interact with PF4 5. Inactivate fibrin-bound thrombin and fluid-phase thrombin 6. Direct inhibitors 1. Lepirudin FDA approval for the treatment of HIT 2. Argatroban 3. Bivalirudin Alternative to heparin for the treatment of PCA

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ARGATROBAN - Novastan

• Synthetic small molecule, derived from arginine • Direct thrombin inhibitor • 1/2 life of 30 -40 m inu tes • Metabolized by the liver • Approved for use in HIT

Assay Insensitivity:

• Many reagents are insensitive to DTI’s • The APTT reagent should be tested to determine where the insensitivity occurs • For many reagent at 0,8mg/L the reagent is flat • Leads to a potential to miss overdosing a patient • Spike PNP with known concentrations of DTI and run the APTT

Jensen, R., (2003), Novel used in the Therapy of Thrombotic Disease, Clinical Hemostasis Review, 17 (8) 1-6.

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APTT versus ARGATROBAN

Argatroban spike versus APTT

70

60

50

40 (seconds) 30

APTT: APTT: 20

10

0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Argatroban (ug/ml)

Castellone, DD., Peerschke, EIB,(2006)A chromogenic method for quantitation of direct thrombin inhibitors: A case study, ISTH, abstract, Geneva,

Using the ACT to monitor levels versus Bivalirudin Levels

600 18

16 500 14

400 12

10 300 g/ml seconds) (

8 u

ACT 200 6

4 100 2

0 0 0 50 100 150 200 Time (minutes)

Castellone, DD., Peerschke, EIB,(2006)A chromogenic method for quantitation of direct thrombin inhibitors: A case study, ISTH, abstract, Geneva,

What do direct thrombin inhibitors do? • PT/INR, APTT prolonged, remain prolonged in mix • Acts like an inhibitor in clotting-time assays, under-estimating results • Fibrinogen falsely low • C & S, overestimated • ATIII - has “anti-thrombin” activity, Increased- • Heparin - anti-Xa, is okay, unless IIa

Walenga, J., (2006) Direct Thrombin Inhibitors & Laboratory Monitoring Issues, Coagulation Symposium, Indianpolis, May 5.

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Argatroban Laboratory Monitoring

• aPTT was recommended to be used: – Baseline aPTT performed 2 hours after infusion is started – aPTT range 1.5-3.0 times baseline – Further studies have demonstrated that this is reagent dependent, APTT can flatten out and not reflect an increased dose, can have dangerous outcomes

• Ecarin clotting time – Linear, may be substituted when APTT is not usable • Activated clottingg() time (ACT) – Used during very high levels of Argatroban during percutaneous cardiac intervention – Maintain ACT 300-450 seconds – We did not find this to be true, we also found a flattening of the results

• PT/INR cannot be used to monitor Argatroban therapy • Thrombin time is not linear and can not be used to monitor Argatroban therapy • When switching from Argatroban to Coumadin, the INR may not be reliable – Therefore a chromogenic Factor X should be used until the patient of off of Argatroban

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Prothrombinase Induced Clotting Time (PiCT)

1. PiCT® is based on the inactivation of FXa 2. Thrombin generation is the final assay reaction 3. Direct thrombin inhibitors produce a concentration dependent effect 4. Time to clot is proportional to drug concentration – Standard curves must be generated for each drug to be assayed

Advantages and Disadvantages of PiCT Assay

• Advantages – Can potentially facilitate monitoring of • LMWH, UFH, Fondaparinux, DTI’s – High sensitivity • Wide measuring range for all anticoagulant agents – Allow analysis of samples in • Prophylactic, therapeutic, and supratherapeutic phase dose ranges – Detects FXa and FIIa inhibition independently of earlier stages of the coagulation cascade • High inter and intra-assay precision – Excellent reagent stability • Disadvantages – Affected by significant deficiencies of FII, FV and fibrinogen • Levels < 25% of normal • May be affected by anti-vitamin K therapy – May be affected by lupus anticoagulants

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Ecarin Clotting Time

• Can be used to monitor DTI's – Not affected by heparin or Warfarin therapy – Superior responsiveness and specificity compared to the APTT • Cannot be used to monitor UFH, LMWH, Fondaparinux • Reagent poorly standardized with increased lot variability • Limited availability; no kit available • No manufactured calibrators or controls

http://content.karger.com/ProdukteDB/produkte.asp?Aktion= ShowPDF&ArtikelNr=81505&Ausgabe=230521&Produkt Nr=224034&filename=81505.pdf

Ecarin Clotting Time

• Ecarin is a thrombin-like snake venom • Ecarin converts prothrombin to meizothrombin which forms 1:1 complexes with r- • Meizothrombin is neutralized by DTI's but not affected by heparin or AVK • Free meizoprothrombin stimulates the conversion of fibrinogen to fibrin • Ecarin clotting time is prolonged with increasing amounts of r-hirudin

Anti IIa assay

• Thrombin is added in excess to the diluted patient plasma. • Thrombin activity is neutralized in proportion to the amount of DTI contained in the sample. • The remaining amount hydrolyses the chromogenic substrate. • The pNA used to promote a color reaction is released upon hydrolysis of the substrate and the released color is then measured photometrically at 405nm. • The amount of residual thrombin activity is inversely proportional to the amount of DTI in the sample.

Package inserts Chromogenix reagents

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Transitioning Patients from Argatroban to Warfarin • Used in treatement of HIT • ARGATROBAN elevates the PT disproportionately; reasons unknown • Treat concurrently until INR is therapeutic about 4-5 days • However, “true” INR is not known • Can use a conversion method provided in ARGATROBAN product labeling

Chromogenic X assay

• Chromogenic X assay measures the amount of factor X • Levels of 11-42% inversely correlate with INRs of 2-3.5 • Levels <11% predict an INR of 3.5 and >42% predict and INR <2.0 • Considered and INR value absent of argatroban if D/C 4 hours, and APTT decreased to 1.5 times baseline or < 40 seconds • Demonstrates 93% sensitivity and 78% specificity

Arpino,PA, Demirjian,Z., VanCott, EM, (2005) Use of the Chromogenic Factor X Assay to Predict the INR, Pharmacotherapy, 25(2):157-164.

Pentasaccharides

• Fondaparinux • Idraparinux* – Plasma half-life 14-24 –Plasma half-life—130 hours hours – 1X/day dosing via – 1x/week via subcutaneous subcutaneous injection injection* – Contraindicated in patients – Contraindicated in patients with severe renal with severe renal insufficiency insufficiency – Does not bind to platelets – Does not bind to platelets or PF4 or PF4 – No antidote – No antidote – 50-fold higher binding • Uncontrolled bleeding affinity for Xa may be treated with – More highly sulfated recombinant Factor VIIa derivative of Fondaparinux – 2.5 mg SC daily • 5-9 days

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Fondaparinux (Arixtra)

• Pentasaccharide • Approved to DVT and PE • Mechanism – Contains the unique pentasaccharide sequence – Binds to activated factor Xa – Inhibits Factor Xa • Indirect inhibitor of IIa

NEJM 52

Pharmacology of the Pentasaccharides • Predictable dose response – Administered 1x/day – Does not bind PF4 or plasma proteins – Monitoring “unnecessary” • Peak activity – 3 hours • No antidote, protamine ineffective – Most common adverse reaction is bleeding – Excreted by the kidneys • IditiIndications – Orthopedic Perioperative DVT prophylaxis •Hip Fracture • Hip replacement • Knee replacement

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Pharmacology of the Pentasaccharides • Contraindications (due to bleeding risk) – Patients with severe renal impairment – Patients weighing less than 110 pounds • Complications – Bleeding • Similar safety to LMWH – Spppyinal thrombosis with risk of paralysis • Associated with concurrent spinal anesthetic procedures

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Additional Contraindications with Pentasaccharides • Patients with Renal disease – Kidney only route of excretion • Patients weighing less than 50 kg • Patients over 75 years old • Patients with any bleeding history – CilidlhiCongenital or acquired coagulopathies – Ulcerative gastrointestinal disease – Hemorrhagic stroke • Patients with history of HIT – Despite no reaction with PF4*

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Dosing and Laboratory Monitoring of Fondaparinux

• Chromogenic Heparin assay based on anti-Xa activity • Requires a calibration curve using Fondaparinux • aPTT is insensitive for monitoring • Monitoring not needed in uncomplicated cases • Collect blood 4 hours after administration • Target range—0.14-.019 mg/L

• Consider monitoring – Infants and children – Obese and underweight patients – Renal disease Exceptions – Long-term treatment – Pregnancy – Unexpected bleeding or thrombosis

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Dabigatran Etexilate • OAC with several advantages over Warfarin and Enoxaparin – Pro-drug Dabigatran is rapidly converted to its active form • Specifically and selectively inhibits both free and clot bound thrombin • PditblPredictable an d cons itthistent pharmaco kitikinetic pro file • Not significantly affected by interactions with food • Eliminated mainly via the kidneys • Not metabolized by cytochrome P450 system – Does not affect the metabolism of other drugs that utilize this system – Leads to a lower potential for drug interactions

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Dabigatran

• Half-life is 14-17 hours • 12 hours after a dose – ~ 50% of the drug is gone – ~75% is excreted within 24 hours of the last dose • Generally does not require monitoring – INRs should not be used as a measure of the anticoagulant effect – Modest elevation of INR, variable and cannot be predicted – aPTT can provide a qualitative indication of anticoagulant therapy – aPTT prolongation is linearly related to the square root of the plasma concentration which should not be used for a for precise quantification of effect – Ecarin clotting time is a specific test that shows a close linear correlation with the plasma • Has the potential to offer physicians and patients a simple and convenient alterative to the present anticoagulant options

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Apixaban

• Oral, direct, selective factor Xa inhibitor • Produces concentration-dependent anticoagulation • No formation of reactive intermediates • No organ toxicity • Low like lihoo d o f drug in terac tions • Good oral bioavailability • No food effect • Balanced elimination (~25% renal) • Half-life ~12 hrs

59 He et al., ASH, 2006, Lassen, et al ASH, 2006

Conclusion

UFH LMWH DTIs Fondaparinux APTT Poor dose Too insensitive “Plateau effect” response Anti FXa Linear over Rx Linear over Rx Not applicable range range Anti FIIa Poorly Not applicable Poorly standardized responsive ECT Non reactive Non reactive Linear over Rx and interventional range PiCT Linear over Linear over Linear over prophylactic, Rx prophylactic, Rx prophylactic, Rx interventional interventional ranges interventional ranges ranges

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Case Studies

How to use the D-dimer assay

Clinical Utility of D-dimer

• Disseminated Intravascular Coagulation (DIC) Simultaneous formation of thrombin and plasmin Sensitive, but not specific marker for DIC • Venous Thromboembolism (VTE) High negative predictive value for exclusion • Potential positive predictive value Positive predictive of recurrent MI Independent predictor of ischemic heart disease Differentiate between a traumatic spinal tap or a subarachnoid bleed Predictor of VTE recurrence, elevated levels following discontinuation of anticoagulant therapy associated with recurrence

Diagnostic Utility

• If you have a D-dimer test that has been cleared by the FDA for exclusion, that test can be used to rule out DVT and PE for non-high clinical pre-test probability assessment model to exclude DVT and PE. • Outpatient setting • To achieve this claim the FDA requires: 1. To establish the cutoff study of the assay (0.500 mg/L) by testing samples against a predicate to verify sensitivity 2. To prospectively collect and enroll patients suspected with PE and or DVT (first time event) and compared standard of care results (imaging) versus the D-dimer result. 3. Negative D-dimer patients receive a 90 day follow up call to evaluate potential development of a PE or DVT 4. Sufficient patients must be enrolled have a >99% NPV to be approved as an exclusionary claim by the FDA.

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Clinical Model to aid in assessment & diagnosis:

• Developed by Wells and colleagues • Based on symptoms and signs for DVT and PE • Presence or absence of an alternate diagnosis • Presence and number of risk factors • Patients are scored based on a series of criteria Scoring for DVT Scoring for PE High probability >/= 3 High probability >6 Moderate 1 or 2 Moderate 2-6 Low

Clinical Model for Predicting DVT Pre-Test Probability Questionnaire Score Active cancer 1 Paralysis, paresis or recent plaster immobilization of lower 1 extremities Recently bedridden > 3d or major surgery w/in 4 wk 1 Localized tenderness alonggp the distribution of deep venous 1 system Entire leg swollen 1 Calf swelling 3 cm > asymptomatic side (measured 10 cm 1 below tibial tuberosity) Pitting edema confined to the symptomatic leg 1 Collateral superficial veins (nonvaricose) 1 Alternative diagnosis as likely or greater than that of DVT -2

Wells, et al. Lancet, 1997;350:1795-1798

Clinical Model for Predicting PE Pre-Test Probability Score

Clinical symptoms and signs of DVT (leg 3.0 swelling and pain) No alternative diagnosis is more likely than PE 3.0 Heart rate > 100 beats/min 1.5 Immobilization or surgery previous 4 weeks 1.5 Previous DVT/PE 1.5 Hemoptysis 1.0 Malignancy (treated within previous 6 months) 1.0

Wells, PS, et al Ann Intern Med 2001;135:98

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Case study

• A 52 year old male comes into the ED complaining of pain in the right calf • Leg is slightly swollen, patient is concerned they may have a blood clot • Otherwise healthy male, not on any , active • Pain seems to have worsen through the night • Wells scoring is a low PTP • ED physician orders a D-dimer • Result is negative (0.345 mg/L) • Should this patient have imaging to rule out the possibility of a DVT?

Case Study

• Good subject to perform D-dimer for rule out claim. • Healthy, not “older” population • Low PTP • D-dimer result not near the cutoff (result is .345 mg/L, cutoff 0 .500 mg/L) • Even knowing the CV of the test (<5% at this level) would not bring the result into the positive range of > 0.500 • May suggest follow up with physician- if pain worsens • Most likely a strain due to sliding into the bases while playing softball!

Case Study: • A 76 year old male patient has been admitted into the ED for an infection • After performing an APACHE assessment, it is determined that he is critically ill, possibly septic • He has a history of DVT so a D-dimer is ordered • Has a high PTP with the Wells score • D-dimer is positive 6.4 mg/L • Does the patient have a blood clot?

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Clues:

• Older patient, septic, previous history of DVT

• Wells scoring results in a high PTP

• What is the utility of an elevated D-dimer?

• What are you looking for?

Case study

• This patient has all the reasons to have a positive D- dimer • Older, septic with previous history of DVT • We don’t know specifically why it is increased • There are many reasons • Not the patient population to be using the D-dimer test to determine a DVT • The patient may be in DIC

Case study

• 42 year old male enters the ED complaining of rapid onset, shortness of breath, pain in chest, numbness in arm • Wells score is mod PTP • Should this patient be imaged for a PE? • D-dimer is normal 0.411mg/L • Additionally testing included an elevated troponin and BNP • Does this person have a PE?

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Case study

• Patient test results appear to be more consistent with an MI, versus a PE • Imaging doesn’t seem to be indicated at this time • Patient is then admitted • Foll ow up w ith imag ing if symp toms s till pers is t severa l days post admission • D-dimer will most likely be elevated as an inpatient, and imaging would be the more diagnostic approach.

Case Study • A 25 year old pregnant female in her second trimester comes into the ED • She is complaining of pains in her leg, leg is slightly swollen • No history of DVT, Wells scoring is low- moderate PTP • Run a D-dimer • The D-dimer test is 0.534 mg/dL (cut-off is 0.500 mg/dL)

• They perform imaging and the imaging is negative

Case Study

• Why did the clinician choose to perform imaging? Patient is an outpatient, has a low PTP

• Why was the D-dimer positive? Positive D-dimer during pregnancy

• However, pregnancy is a hypercoagulable state, and pregnant patients are usually excluded from studies

• Best to perform imaging on this patient

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Case Study

• A 40 year old male comes into the ED complaining of sudden onset of shortness of breath • He has had a cold for 2 days, but now feels a heaviness in his chest • He does have a history of asthma • The clinician suspects that he might have pneumonia, but wants to make sure he doesn’t have a PE • Performs a D-dimer, which is negative • Doesn’t order a VQ scan, treats the patient, gives him medication with orders to follow up with his family physician next week. • Did he do the right thing?

Case study • The laboratory used an automated immunoturbidimetric D- dimer assay • This assay has been FDA approved for exclusion for PE • A prospectively collected clinic trial looking at over 1000 patients suspected of DVT and or PE were tested and imaged and their imaging results were compared to the D- dimer • A negative predictive value of >99% was determined • This results in being able to have patients with a low- moderate pre test probability and a negative D-dimer not have to be imaged. • This patient’s diagnosis was asthmatic bronchitis, did not have to have expensive imaging, D-dimer was able to provide a diagnosis

Pearls for Practice:

• Understand the utilization of the D-Dimer in diagnosing patients with a low PTP for DVT or PE • The value in having a test with an exclusion claim and the outcome for enhanced patient care: » Less invasive testing » Decreased risk to the patient » Decreased time from testing to diagnosis

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Thank you for your time – any questions?

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