Table 2.
Prevalence of Tunisian individuals expressing the weak D type 4.0 phenotype *
| Parameter | Number of donors | Frequency as published | References and calculations | |
|---|---|---|---|---|
|
| ||||
| Rate | Fraction | |||
| Donors (all) | 13,431 | n/a | n/a | This study |
| RhD antigen negative RH haplotypes | n/a | 0.3021 | 1 : 3.31 | cde = 0.284, Cde = 0.018, cdE = 0.0001 36 |
| Weak D type 4.0 positive RH haplotypes | n/a | 0.0095 | 1 : 105.26 | 2,000/19 = 105.26 †12 |
| Donors with weak D type 4.0 phenotype * | ||||
| Expected (calculated) | 77 | n/a | n/a | 13,431 × (0.3021 × 0.0095) × 2 = 77.25 ‡ |
| Observed (RHD sequence confirmed) | 53 | n/a | n/a | This study |
*
These individuals must be hemizygous for an RH haplotype with a functional RHD allele on 1 chromosome (i.e., no functional RHD allele on the other chromosome).
†
Among 1,000 random donors, including RhD negative donors and representing 2,000 RH haplotypes, a total of 19 donors were found carrying a weak D type 4.0 allele.12
‡
The frequency of an RhD antigen negative RH haplotype paired with the weak D type 4.0 positive RH haplotype must be multiplied by 2, because this haplotype combination can occur in 2 ways for the pair of chromosomes in a given donor.