Catherine P. M. Hayward, MD PhD FRCPC Professor, Pathology & Molecular Medicine, & Medicine, McMaster University Head, Coagulation, Hamilton Regional

Transcription

1 Catherine P. M. Hayward, MD PhD FRCPC Professor, Pathology & Molecular Medicine, & Medicine, McMaster University Head, Coagulation, Hamilton Regional Laboratory Medicine Program

2 No relevant disclosures for this presentation Slides showing figures with unpublished data and details of ISTH LTA recommendations have been removed from this presentation

3 Name diagnostic tests most useful for diagnosing platelet function disorders (PFD) least two major challenges to external quality assurance (EQA) for platelet function tests Give examples two types of EQA used for platelet function tests Be familiar with the purpose of North American guidelines on platelet aggregometry why the guidelines include recommendations on aggregometry interpretation

4 Important cause of abnormal bleeding but challenging to diagnose Most recent Hamilton prospective cohort study 2 von Willebrand disease - 30 inherited platelet disorders Heterogeneity in PFD pathogenesis Largely unknown, especially for common PFD Possibilities are enormous Platelets > 1000 proteins Megakaryocytes transcribe many more genes

5 Diagnostic tests No simple approach or kits Require rapid processing and testing of freshly collected blood samples Not optimally standardized, interpreted Only recently evaluated by EQA or workshops

6 Adhesive receptors Agonist receptors

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8 Established and emerging evidence: Sometimes need platelet transfusion management Bleeding risks similar to von Willebrand disease Likelihood, as Odds Ratios ~ for different bleeding problems M. Pai, CHAT study to be presented at ISTH 2011

9 Essential CBC warning: doesn t always exclude thrombocytopenic PFD, e.g. RUNX-1 defects Aggregometry light transmission (LTA) and whole blood methods Optional PFA-100 Not Recommended Bleeding time can t be controlled, minimally informative

10 Dense granule assays Content release often assess: adenosine triphosphate (ATP) release by lumi-aggregometry Contents include ATP, ADP, serotonin, calcium and phosphorous Electron microscopy (EM) or meparine quantify numbers of dense granules NASCOLA Platelet EM EQA all labs have properly diagnosed dense granule deficiency Hayward et al, Am J Clin Pathol. 2009;131:671-5 Genetic tests specific disorders, prevalent in some populations Other assays?

11 % MA Evaluate results according to reference intervals for: 1) maximal aggregation (MA) evaluated by light transmittance (or impedance if using whole blood) 2) ATP release (nm), evaluated by luciferin/luciferase method (using an ATP standard) d-luciferin +ATP Firefly luciferase Oxyluciferin + AMP + light Strong agonist: immediate ATP release Weak agonist: ATP release with 2 o aggregation Aggregation 6 mm epinephrine 5 mg/ml collagen ATP release ATP release is delayed and less complete with epinephrine

12 Strongest evidence of needs for PFD test standardization

13 CLSI Guideline Christie DJ, et al. Platelet function testing by aggregometry. CLSI document H58-A. Wayne, PA: CLSI, 2008 NEW: North American guidelines (include LTA interpretation) Hayward CP, et al. Development of North American consensus guidelines for medical laboratories that perform and interpret platelet function testing using light transmission aggregometry AJCP 2010;134: ISTH Guidelines 1. Hayward CP, et al. Platelet function analyzer (PFA)-100 closure time in the evaluation of platelet disorders and platelet function. J Thromb Haemost 2006;4: In progress: ISTH expert consensus guidelines on LTA practices BSH (expected soon)

14 Used Rand method for when evidence is limited Int J Technol Assess Health Care 1986;2:53-63 Experts Selected Cattaneo, Italy; Hayward, Canada; Harrison, UK; Kenny, UK; Michelson, USA; Nugent, USA;Watson, UK; Cerletti, Italy; Nurden, France; Rao, USA; Schmaier, USA Consulted, voted on statement appropriateness Likert scales, comment boxes Discard two extreme scores majority vote

15 LTA is clinically useful for studying subjects with bleeding disorders should NOT be used for identifying subjects at risk for thrombosis monitoring subjects on anti-platelet therapy Dr. Kottke-Marchant will update information on this next

16 Final agonist concentrations: practices versus recommendations from JTH 2009;7:1029, CLSI guidelines, QMPLS Broadsheet; AJCP 2010;134: Agonist % clinical labs using for LTA ISTH Survey Clinical labs Median (range) North American Guideline Recommendations CLSI Recommendations ADP (mm) 100% 5.0 ( ) often 5 to start Collagen (mg/ml) - 78% use type I fibrillary 2.0 ( ), low concentration that detects NSAID 1-5, often 2 to start abnormalities Epinephrine (mm) 72% 7 ( ) Typically 5 to start Ristocetin (mg/ml) - Low dose 80% High dose 82% 0.5 ( ) 1.5 ( ) Arachidonic acid (mm) 82% 1.36 ( ) Optional Thromboxane analogue U46619 (mm) - 15% 1.0 ( ) 1.0 (QMPLS) Optional: 1-2 TRAP (mm) - 17% 10 (1-100) _ Only mentioned

17 Options for evidence-based assessment Association of test result with a clinical problem PFD or a Definite Bleeding Disorder (DBD) Often expressed as an Odds Ratio (OR) Assess test sensitivity and specificity Area under Receiver Operator Curves (AUROC) 1=perfect test Non-inferiority/superiority analysis of tests Differences in AUROC

18 Odds Ratio infinite BT with PFD LTA with Bleeding Disorder LTA with Acquired PFD 10.6 LTA with Inherited PFD Data from Hayward et al, JTH 2009;7; Dense Granule Deficiency by EM (one subtype of PFD)

19 better worse From Hayward et al, JTH 2009;7; A limited panel of agonists detects most common PFD (epinephrine, AA, thromboxane analogue, 1.25 mg/ml collagen) Larger panel is needed to detect rare disorders

20 Test A better Test B better Difference is acceptable _ 0 Estimate differences in AUROC

21 Key findings: Quiroga et al, Br J Haematol 2009;147: Normal : 93.3% confirmed Abnormal: 90.4% confirmed

22 Abnormalities in maximal aggregation (MA) All agonists combined Odds Ratio (95% CI) for association with PFD (subjects without thrombocytopenia and VWD) Inherited PFD Acquired PFD Only one agonist abnormality Two or more abnormalities 2.3 ( )* 78 (11-605) 0.6 ( )* 39 ( ) From JTH 2009;7; Unpublished: Single agonist abnormalities (except with ristocetin, perhaps collagen) are often not confirmed by repeat testing 22

23 Serotonin release - few labs now perform (radioactive) Quiroga et al, Br J Haematol 2009;147: Most aggregation defects are associated with release release occurs in some bleeders with normal aggregation (14.3%) ATP release - measured by lumiaggregometry Principle: Uses a reagent containing D-luciferin, luciferase light emission triggered by released ATP Glasson and Fritsma STH 2009 ;5: Cattaneo STH 2009 ;5:158-67

24 Abnormality associations Odds Ratio (95% CI) Bleeding disorder 17 (6-46) Inherited platelet disorder 128 (30-545) Inherited platelet disorder, LTA normal 105 (20-545)

25 ROC for ATP release defects (abnormalities with one or more agonists) Most abnormalities detected by a few agonists 6 μm epinephrine, 5.0 μg/ml collagen 1 mμ U46619

26 Paterson et al Blood 2010;115: Test for PLAU (upa gene) duplication mutation Use new cases diagnosed in both Canada and USA in Quebec, prevalence of QPD > type 2B VWD Future? - CHIPs to test for a variety of inherited PFD

27 Engage participants Discussions, lectures, etc can include wet or dry test exercises Examples Development of North American LTA Guidelines In person (QMP-LS), virtual (NASCOLA) Wet workshop on PFD e.g. 7th ECAT Participants Meeting, 2010

28 Hackeng, Eikenboom, Verbruggen, Meijer 7th ECAT Participants Meeting, participants, 5 Groups 8 Patients: 4-5 tested per group Platelet function measurements in whole blood with: PFA-100 Chronolog Impedance and Luminescence Multiplate VerifyNow St. Antonius Center for Platelet Function Research

29 Virtual Dry workshops Results of initial NASCOLA EQA challenges See tremendous improvements: poster #811 by Moffat et al Tracings, results and RI for interpretation were distributed to NASCOLA and ECAT labs Case Diagnoses, First EQA Challenges % correct interpretations Normal ~92% Rare but well characterized disorder (e.g. Glanzmann thrombasthenia, Bernard Soulier Syndrome) ~85% Common defect with multiple aggregation abnormalities (e.g. Secretion defect, dense granule deficiency) ~33% False positive/non-diagnostic findings ~18-44% Normal variant ~16%

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31 LTA Finding Aggregation absent or marked with AA, normal with U46619, with low dose collagen. Aggregation is present with only ristocetin. Recommended Interpretation QMPLS and NASCOLA Aspirin-like defect (drug induced or inherited). Possible Glanzmann thrombasthenia (inherited or acquired). Follow-up Investigation Repeat testing when subject not on aspirin or other NSAIDs. Glycoprotein analysis of fibrinogen receptor alphaiib-beta3. Aggregation absent with high conc. of ristocetin and the patient has thrombocytopenia with very large platelets. Aggregation with high conc. of ristocetin without thrombocytopenia. Aggregation abnormally with low conc. of ristocetin. Aggregation abnormal with multiple agonist. Markedly with ADP with significant deaggregation. Other abnormalities with two or more agonists. Possible Bernard Soulier Syndrome (inherited or acquired). VWD should be excluded. Possible von Willebrand disease. Possible type 2B or platelet-type VWD. Possible platelet ADP receptor defect (P2Y12). Drug induced defect should be excluded. Suggest a platelet function disorder is present. Confirm on repeat testing. Glycoprotein analysis to assess glycoprotein IbIXV, the VWF receptor. VWF levels. VWF levels. Consider genetic testing. Repeat aggregation testing. Platelet ATP release and/or EM for dense granule deficiency (DGD). Abnormalities with only one agonist (excluding collagen or ristocetin). Non-diagnositic and could represent a false positive. Repeat aggregation testing, ATP release and/or EM for DGD.

32 Examples of some pitfalls if testing is limited Case 1 No challenges, very large bruises, heavy periods Case 2 Bruises, serious bleeding with surgery Case 3 No major challenges but relatives have bleeding problems including joint bleeds ADP 2.5 mm Normal Normal Normal ADP 5.0 mm Normal Normal Normal Collagen 1.25 mg/ml Normal Normal Collagen 5.0 mg/ml Normal Normal Epinephrine 6 mm Normal Normal Arachidonic acid 1.6 mm Normal Normal Thromboxane analogue U mm (few labs test) Ristocetin 0.5 mg/ml Normal Normal (<7% aggregation) Normal (<7% aggregation) Normal (<7% aggregation) Ristocetin 1.25 mg/ml Normal Normal Normal LTA Interpretation Findings suggest a platelet function disorder (aspirin-like defect excluded) Non-diagnostic Non-diagnostic Diagnosis after other tests Dense granule deficiency Secretion defect based on abnormal ATP release Quebec platelet disorder based on genetic tests

33 Colleagues and Collaborators HRLMP Special Coagulation NASCOLA QMPLS ISTH SSC