From Ravinda (Ravi) Sarode, MD, Chief of Pathology, University of Texas Southwestern Medical Center, Dallas. Hey George, sorry for late response.
I have used WBA since 1987! I have made comparisons between the two methods and every time found WBA more sensitive. One example I will quote is a patient with CLL who had easy bruising and retinal hemorrhage. Three times the WBA produced abnormal results to AA, collagen and ADP. went to Paul Bray at Jefferson, who ran LTA and showed normal aggs. I then ran both WBA and PRP simultaneously and showed that LTA was normal and WBA was again abnormal. What could be the reason? I have no idea–suspect red cells modifying the platelet aggregation. We had a similar case in a child who was on an anti-epileptic drug that is known to affect plt function. The child had normal aggs on LTA and abnormal on WBA performed simultaneously. We recently published our experience in Neurology where we check ASA and Plavix effect before taking the patient for coil placement in aneurysm and showed a better outcome as compared to era when we did not.
I agree that ADP-induced ATP secretion is not good and hence we don’t do it. Thrombin, AA and collagen give the same info about secretion. We also have seen many patients on selective serotonin reuptake inhibitors (SSRI) who have acquired platelet dysfunction. Glanzmann thrombasthenia (GT) is reproducible in LTA and WBA; especially acquired GT. We have not seen BSS. For type 2B VWD we have no problems detecting it with RIPA.
Also, not many people believe in hyperactive platelets but we do. We have shown in many cases, especially myeloproliferative neoplasms, that they have mixed responses–hyperactive to some agonists and hypoactive to others. This might help tailor therapy. Like everything in medicine we all have personal preferences. For example people still do routine PTT mixing studies! We don’t–we are Canadian in that regards! Ravi.