Molecular methods

Question 1

what are two types of HLA B27 testing? And list their advantages and disadvantages

Answer 1

Method 1) Flow cytometry
Advan: fast TAT, easy, cheap, less labour intensive, integrate existing flow platform, low volumes required
Diadvan: issues with mAb specificity for HLA B27/cross reactivity with B7 groups, need fresh cells, need to obtain controls (?commerical)

Method 2) Nucleic acid testing (PCR, SSOP)
Advan: high specificity, gold standard, no need fresh cells/issue w cross reactivity
Disadvan: slow TAT, expertise/molecular lab, expensive

Method 3) CDC
Advan: well validated, cheap, nil cross reactivity with high affinity antibodies
Disadvan: fresh cells, expensive, slow , expertise, subjective interpretation

Question 2

What are some of the issues with HLA B27 flow cytometric testing?

Answer 2

• lack of monospecifici hla b27 antibodies (CRG cross reacting group) with B7 and non B7 CRG
• antibodies react variably with different HLA b27 alleles
• most labs two antibodies- combi7 screen and b7/1-lamba confirmatory so the cross reactive profiles dont overlap