Unrelated CB unit selection guidelines
| . | Guidelines . |
|---|---|
| Bank practices | |
| Attached segment identity testing | Mandatory |
| Use of RBC-replete units*† | Not recommended |
| Cryovolume‡ | Should be considered, especially if the unit is to be diluted post thaw |
| Year of cryopreservation | More recent units may be linked to optimal banking practices depending on the bank |
| Bank location | Domestic or international units fulfilling selection criteria |
| Bank accreditation and/or licensure | Should be considered |
| HLA match | |
| Resolution of HLA typing | Minimum of 8 high-resolution (HLA-A, HLA-B, HLA-C, and HLA-DRB1) for both patient and CB unit |
| Donor–recipient HLA match | ≥4/6 HLA-A and HLA-B antigen, HLA-DRB1 high-resolution (traditional match), and ≥4/8 high-resolution match (some centers investigating use of 4/6 and 3/8 units if adequate dose) |
| Unit–unit HLA match for double unit CBT | Not required |
| Avoidance of units against which recipient has DSA§ | Conflicting results in hematological malignancies; avoid if nonmalignant diagnosis |
| Cryopreserved cell dose||¶# | |
| Single-unit CBT: minimum dose/kg | TNC ≥2.5 × 107/kg and CD34+ cells ≥1.5 × 105/kg (some centers recommend higher CD34+ dose as minimum) |
| Double-unit CBT: minimum dose/kg per unit | TNC 1.5 × 107/kg for each unit and CD34+ cells ≥1.0 × 105/kg for each unit (some centers recommend higher CD34+ doses for each unit as minimum) |
| . | Guidelines . |
|---|---|
| Bank practices | |
| Attached segment identity testing | Mandatory |
| Use of RBC-replete units*† | Not recommended |
| Cryovolume‡ | Should be considered, especially if the unit is to be diluted post thaw |
| Year of cryopreservation | More recent units may be linked to optimal banking practices depending on the bank |
| Bank location | Domestic or international units fulfilling selection criteria |
| Bank accreditation and/or licensure | Should be considered |
| HLA match | |
| Resolution of HLA typing | Minimum of 8 high-resolution (HLA-A, HLA-B, HLA-C, and HLA-DRB1) for both patient and CB unit |
| Donor–recipient HLA match | ≥4/6 HLA-A and HLA-B antigen, HLA-DRB1 high-resolution (traditional match), and ≥4/8 high-resolution match (some centers investigating use of 4/6 and 3/8 units if adequate dose) |
| Unit–unit HLA match for double unit CBT | Not required |
| Avoidance of units against which recipient has DSA§ | Conflicting results in hematological malignancies; avoid if nonmalignant diagnosis |
| Cryopreserved cell dose||¶# | |
| Single-unit CBT: minimum dose/kg | TNC ≥2.5 × 107/kg and CD34+ cells ≥1.5 × 105/kg (some centers recommend higher CD34+ dose as minimum) |
| Double-unit CBT: minimum dose/kg per unit | TNC 1.5 × 107/kg for each unit and CD34+ cells ≥1.0 × 105/kg for each unit (some centers recommend higher CD34+ doses for each unit as minimum) |
Developed by the ASBMT CB Special Interest Group. For successful engraftment, optimal CB graft selection and the patient’s rejection risk must be considered.9
CBT, CB transplant; RBC, red blood cell; TNC, total nucleated cell.
RBC-replete units have been associated with life-threatening infusion reactions. Washing is difficult due to the lack of a clear interface after centrifugation; washing also risks cell loss. Therefore, RBC-replete units should be used with caution. They should only be considered in the absence of RBC-depleted CB units meeting acceptable criteria.
Incorporation of nucleated red cell content in unit selection is not recommended at this time.
Some expert centers prefer to use an RBC-depleted unit that has a post-cryopreservation volume of ∼25 mL/bag. If a unit was divided into 2 bags for storage, then each bag should contain ∼25 mL.
Regarding the significance of HLA antibodies, DSAs must be considered on a case-by-case basis based on diagnosis and prior immunosuppressive therapy that determine rejection risk, the intensity of planned conditioning, and the number, titer, specificity, and complement fixation of DSAs. DSA targeted units should be avoided in nonmalignant diagnoses. In patients with malignancies, avoid if possible, but use caution if avoidance of units against which the patient has antibodies compromises the selected CB unit dose and HLA match.
For single- vs double-unit CB transplant, if no adequate single-unit graft is available, then a double-unit graft is recommended. Clinical trials investigating the addition of other cellular products to a single-unit graft can also be considered.
For prioritization of cell dose vs HLA match (applies to single- and double-unit transplants), cell dose frequently needs to take priority over HLA match for adult and larger pediatric patients. HLA-match can take priority in children or smaller adults or those with common HLA typing who have multiple units with high cell dose. Optimizing HLA-match is very important in CB transplant for nonmalignant diagnoses. In children with nonmalignant diagnoses, higher cell doses (≥5 × 107/kg) should be selected. Further data are required as to how to balance cell dose against HLA match. A current guidance for consideration is as follows: if high doses (eg, TNC ≥3 × 107/kg and CD34+ ≥2 × 105/kg), consider optimizing high-resolution HLA match over cell dose; if lower TNC and CD34+ doses, optimize dose first and high-resolution HLA match second; and if units have similar cell doses, optimize high-resolution HLA match.
Reporting of unit viability testing is not fully standardized. Flow-based assays of CD34+ cell viability on a segment can be informative but have not been validated in multiple banks/centers. The NMDP will facilitate discussion between centers and the bank if questions concerning viability testing arise.