Platelet Transfusions in Stem Cell Transplant Patients — a New Metric and Measurements

Background:

We describe a new metric (transfusion intensity or TI) for assessing platelet transfusion (PT) in stem-cell transplant (SCT) patients. Using this, and conventional metrics, we compare PT in different types of SCT patients.

Methods:

We assessed PT use in autologous- or allogeneic-SCT (auto-SCT, allo-SCT) patients in Christchurch, New Zealand between 2011 and 2015 (n = 176). PT were mainly prophylactic (trigger platelet count < 10 x 10⁹/L). Conventional metrics for PT use included:

1. Total dose (TD) : adult doses (AD) of platelets transfused between days 0 to +180 (those dying by day +180 were included).

2. Duration : number of days between first and last PT.

3. Crude transfusion rate (CTR): TD divided by duration.

A new metric is described:

1. TI : the product of CTR and TD . This allows differentiation between PT use with overlapping features - for instance, in patients needing

• similar TD over different durations e.g. (a) 5 AD over 5 days versus (b) 5 AD over 10 days

• different TD over similar durations e.g. (b) versus (c) 10 AD over 10 days.

TD, duration, CTR, and TI, respectively, would be 5, 5, 1, and 5 in (a); 5, 10, 0.5, and 2.5 in (b); 10, 10, 1, and 10 in (c).

Results:

Complete data was available on 173/176 patients (except for CD34 dose for which data was available on 172). Males and females were 97 (56.1%) and 76 (43.9%) respectively. Ten (5.8%), 17 (9.8%), 84 (48.6%), and 62 (35.8%) patients were respectively in age groups ≤ 20, 21 - 40, 41 - 60, and ≥ 61 years. Auto-SCT and allo-SCT, respectively, were performed in 128 (74%) and 45 (26%) patients. Of the 45 who had an allo-SCT, 23 and 22 respectively (13% and 12% respectively of the total) had either graft-host-disease (GVHD) or no GVHD. CD34 doses (x 10⁶/kg) were as follows: range, 0.9-19.4; mean [SD], 5.3 [3.0]; median [IQR], 4.6 [3.5-6.3]. Thirty one (18%), 92 (53.5%), and 49 (28.5%) had CD34 doses (x 10⁶/kg) of ≤ 3.0, 3.1-6.0, and ≥ 6.1 respectively.

Auto-SCT was performed for various conditions - myeloma (76), NHL (31), and Hodgkin's disease (10) were commonest. Allo-SCT was most often performed for AML (16), ALL (7), and myelofibrosis (5).

For all patients together, range, mean [SD], median [IQR] for TD were 0-55, 4 [7], 2 [1-4]; for duration, 1-177, 17 [33.1] 4 [1-10.5]; for CTR, 0-2, 2.7 [6.5], 0.7 [0.4-1]; and for TI, 0-73.8, 2.7 [6.5], 1.3 [1-2.3].

TD, duration, TI in auto-SCT patients were significantly lower than in allo-SCT patients (P= 0.001, 0.01, and 0.0006 respectively, Wilcoxon rank sum test) though CTR was essentially similar (P= 0.7, Wilcoxon rank sum test). TD in auto-SCT patients were ≤ 4 in 93 (72.7%) and ≥ 5 in 35 (27.3%); corresponding figures for allo-SCT patients were 22 (48.9%) and 23 (51.1%) respectively (P= 0.003, Chi-square test). TD, duration, CTR in myeloma patients undergoing auto-SCT were significantly lower than in non-myeloma patients undergoing auto-SCT (P= 0.003, 0.001, and 0.002 respectively, Wilcoxon rank sum test) though TI was similar (P= 0.8, Wilcoxon rank sum test). TD, duration, CTR in patients aged ≥ 41 years were significantly lower than in those aged ≤ 40 years (P= 0.02, 0.002, and 0.01 respectively, Kruskall-Wallis test) though TI was similar (P= 0.9, Kruskall-Wallis test).

No significant differences in any metric of PT use was found based on sex, CD34 dose, conditioning regimen (reduced intensity/myeloablative), GVHD (presence/absence), or ABO- compatibility.

Conclusions:

There is surprisingly little information on PT in SCT patients. A new metric of PT (TI) is described which may prove useful in such patients. Lower PT use was expected in auto-, compared to allo-, SCT patients but lower use in older patients, and in myeloma, compared to non-myeloma, patients undergoing auto-SCT was unexpected. However there are confounding correlations between age, myeloma, and auto-SCT. Using any metric, no differences in PT use were found based on CD34 dose, conditioning, or ABO-compatibility. In our small study we were unable to consider factors such as graft source, graft manipulation, CD34 subsets, co-morbidities, HLA-matching, and platelet refractoriness. Re-evaluation PT use in SCT patients is required.