JPAC Joint United Kingdom (UK) Blood Transfusion and Tissue Transplantation Services Professional Advisory Committee

18.1: Reagent manufacture/reference preparations

18.1.1: HPA typing reagents

  • There are several human platelet antigen (HPA) genotyping and phenotyping techniques. The latter are generally based on the use of polyclonal HPA alloantibodies obtained from immunised donors or patients, or monoclonal antibodies. HPA typing techniques that do not require polyclonal antibodies derived from donors or patients are the techniques of choice.
     
  • HPA typing reagents prepared from human source material should comply with the guidelines in section 11.1.4.10. An ‘Instructions for use’ sheet (package insert) should be prepared and supplied with antibody typing reagents. Information in the ‘Instructions for use’ should further indicate the immunoglobulin class of the antibodies and the presence of any other contaminating antibodies reactive by the recommended methods.
     
  • HPA typing reagents used in genomic DNA and PCR-based techniques should comply with the guidelines in Chapter 14.

18.1.2: Composition of platelet cell panel for HPA antibody detection

  • It is recommended that laboratories make all reasonable efforts to include cells in their panel that will aid the detection and identification of clinically significant HPA antibodies. The panel should consist of platelets typed at a minimum for HPA-1, -2, -3, -5 and -15 by validated HPA typing techniques. Ideally, the panel should contain platelets that are homozygous for HPA-1a, -1b, -2a, -2b, -3a, -3b, -5a, -5b, -15a and -15b and be from Group O donors.
     
  • HPA typing of a platelet panel donor should be based on two concordant typings performed on samples obtained on different occasions. Wherever possible, phenotyping for the above antigens should also be performed on one occasion.

18.1.3: Selection of normal control sera

Normal control sera should be taken from non-transfused group AB male or ABO compatible blood donors. The sera should be screened and found negative for platelet-reactive-antibodies (e.g. clinically non-significant autoantibodies or EDTA-dependent antibodies are occasionally detected in apheresis donors). An appropriate number of normal sera should be used so that a statistically relevant normal range in a given assay can be determined.

18.1.4: Selection of positive control sera

At least one positive control should be included in each assay. The selection and number of positive control sera will depend on the technique and the HPA type of the platelets being used.
In glycoprotein-specific assays a positive control for each glycoprotein used should be included as a minimum.

18.1.5: Reference preparations

  • Sensitivity of techniques should be monitored on the basis of the inclusion of a ‘weak positive’ control. For anti-HPA-1a, -3a and -5b, the internal sensitivity control should be calibrated against the WHO International Reference Reagents for anti-HPA-1a (NIBSC code 05/106), anti-HPA-3a (NIBSC code 03/190) and anti-HPA-5b (NIBSC code 99/666) when diluted as instructed by the manufacturer.
  • In-house sensitivity standards, with similar reaction strengths to the above reagents, should be prepared for anti-HPA-1, -3 and -5, and, if possible, for anti-HPA-2 and -15 antibodies.

Table 18.1 Current HPA nomenclature

System Antigen Original names Glycoprotein CD

HPA-1

HPA-1a

Zwa, PlA1

GPIIIa

CD61

 

HPA-1b

Zwb, PlA2

 

 

HPA-2

HPA-2a

Kob

GPIbalpha

CD42b

 

HPA-2b

Koa, Siba

 

 

HPA-3

HPA-3a

Baka, Leka

GPIIb

CD41

 

HPA-3b

Bakb

 

 

HPA-4

HPA-4a

Yukb, Pena

GPIIIa

CD61

 

HPA-4b

Yuka, Penb

 

 

HPA-5

HPA-5a

Brb, Zavb

GPIa

CD49b

 

HPA-5b

Bra, Zava, Hca

 

 

 

HPA-6bw

Caa, Tua

GPIIIa

CD61

 

HPA-7bw

Moa

GPIIIa

CD61

 

HPA-8bw

Sra

GPIIIa

CD61

 

HPA-9bw

Maxa

GPIIb

CD41

 

HPA10bw

Laa

GPIIIa

CD61

 

HPA11bw

Groa

GPIIIa

CD61

 

HPA12bw

Iya

GPIbbeta

CD42c

 

HPA13bw

Sita

GPIa

CD49b

 

HPA14bw

Oea

GPIIIa

CD61

HPA-15

HPA-15a

Govb

CD109

CD109

 

HPA-15b

Gova

 

 

 

HPA-16bw

Duva

GPIIIa

CD61

 

HPA-17bw

Vaa

GPIIIa

CD61

 

HPA-18bw

Caba

GPIa

CD49b

 

HPA-19bw

Sta

GPIIIa

CD61

 

HPA-20bw

Kno

GPIIb

CD41

 

HPA-21bw

Nos

GPIIIa

CD61

 

HPA-22bw

Sey

GPIIb

CD41

 

HPA-23bw

Hug

GPIIIa

CD61

 

HPA-24bw

Cab2a+

GPIIb

CD41

 

HPA-25bw

Swia

GPIa

CD49b

 

HPA-26bw

Seca

GPIIIa

CD61

 

HPA-27bw

Cab3a+

GPIIb

CD41

18.1.6: Quality control schemes

Laboratories should take part in regular external quality control exercises such as the National Institute for Biological Standards and Control (NIBSC) Platelet Immunology Quality Scheme for HPA antibody detection and for HPA genotyping. Effective mechanisms should be in place to correct poor performance in the quality scheme.

18.1.7: Nomenclature

The current HPA nomenclature must be used for recording platelet-specific alloantigen and alloantibody specificities1 (see Table 18.1). Any subsequent additions can be found in the Immuno Polymorphism Database (IPD) website (www.ebi.ac.uk/ipd/hpa/).