Platelet Function (Patient H&P)

Platelet function can be adversely affected by the following factors

1. Medication (drugs that may cause induction of anti-platelet antibodies)
   1. Analgesics (eg, acetaminophen)
   2. Antibiotics (eg, cephalosporins)
   3. Diuretics
   4. Digoxin
   5. Disulfiram
   6. Heavy metals (eg, gold)
   7. Heparin
   8. Hypoglycemics (oral, eg, chlorpropamide)
   9. Hypnotics (eg, Phenobarbital)
   10. Quinidine
   11. Propylthiouracil
   12.  
2. Kidney disease
3. Liver disease
4. Sepsis
5. Increased fibrin or fibrinogen degradation
6. Cardiopulmonary bypass
7. Primary marrow disorders

It is important to assess signs exhibited in patients with inadequate platelet number or function.  These signs would be:

1. Petechiae
2. Easy bruising
3. Mucous membrane bleeding

A laboratory assay to determine inadequate platelet function would be

1.      Platelet count

2.      Bleeding time (assesses both vascular phase and platelet phase of hemostasis)

3.      Platelet aggregation studies (PlateletWorks)

Platelet Preparation Quality Control Parameters

1. Expected Values
   1. Platelet count ≥5.5 x 10¹⁰ per 60ml sample (6 units) in 75% of components tested
   2. pH ≥ 6.2
2. Testing frequency
   1. Monthly

3. Platelet Life Span and Storage
   1. Platelets must be stored at room temperature (20-24 C)
   2. Re-suspended platelets must have continuous gentle agitation at room temperature during storage. 
   3. Platelets can be stored in the above mentioned conditions for up to 5 days in an approved plastic storage bag (allows breathing)

4. Procedural Documentation
   1. Document times and staff performing collection, and separation

5. Control Documentation
   1. Document monthly platelet counts, platelet concentrate volume and pH on at least 4 units

6. Processing Chambers
   1. Daily manual and recorder temperature checks (if using a cooling chamber, otherwise record room temperature)
   2. Periodic preventative maintenance and cleaning
   3. Periodic check for orderliness
   4. Periodic rotation/oscillation check on rotators

7. Weld Quality Controls
   1. All sterile connection device welds must be inspected for completeness, integrity, leakage and air bubbles

8. Sample Collection
   1. Establish a clean venipuncture site to minimize bacterial contamination
   2. Minimize activation during collection with a rapid and gentle draw
   3. There should be frequent and gentle mixing of the blood with the anticoagulant during the draw
   4. The target collection time is less than 10 minutes
   5. Blood should not be cooled below 20 C for component preparation

9. Platelet Separation Controls
   1. Blood must be at room temperature (20-24 C) before platelet separation occurs
   2. Separation must occur within 8 hours of phlebotomy
   3. Once platelet concentrate have been acquired some plasma should remain on the platelet button for storage, but no exact volume can be designated.  Platelet rich plasma must have a pH ≥ 6.2
   4. Re-suspend platelets by manipulating the platelet container gently by hand
   5. Inspect re-suspended platelets making sure no platelet aggregates are visible and document this finding

10. Platelet Loss
    1. Studies show 5-20% platelet loss in units centrifuged at 5000 X g for 6 minutes or 2000 g for 10 minutes
    2. There is no consensus regarding optimal centrifugation rate

11. Platelet Calculations
    1. Number of platelets in a sample of whole blood

·         WB = platelets/µl X 1000 X ml

·         WB = number of platelets in whole blood

2. Number of platelets in a sample of PRP

·         PRP = platelets/µl X 1000 X ml of PRP

·         PRP = number of platelets in PRP sample

3. Calculate percent yield

·         % yield = Number of platelets in PRP sample X 100 / Number of platelets in whole blood