PFA or Pfa may refer to:

Chemistry and engineering

Computers

Mathematics

Organizations

The Professional Footballers' Association (PFA) is the trade union for professional association footballers in England and Wales. The world's oldest professional sport trade union, it has 4,000 members.

The aims of the PFA are to protect, improve and negotiate the conditions, rights and status of all professional players by collective bargaining agreements.

The PFA is affiliated with the Professional Footballers' Association Scotland. The Northern Ireland PFA disbanded in 1995.

History

The Players' Union

The PFA was formed on 2 December 1907 as the Association of Football Players' and Trainers' Union (the AFPTU, commonly referred to at the time as the Players' Union). On that date, Charlie Roberts and Billy Meredith (who had been involved in the AFU), both of Manchester United, convened the Players' Union at Manchester’s Imperial Hotel.

This was the second attempt to organise a union of professional footballers in England, after the Association Footballers' Union (the "AFU"), formed in 1898, had been dissolved in 1901. The AFU had failed in its objectives of bringing about a relaxation of the restrictions on the movement of players from one club to another in the Football League and preventing the introduction of a maximum wage of £4 per week for players in the Football League.

The PFA-100 (Platelet Function Assay or Platelet Function Analyser) is a platelet function analyser that aspirates blood in vitro from a blood specimen into disposable test cartridges through a microscopic aperture cut into a biologically active membrane at the end of a capillary. The membrane of the cartridges are coated with collagen and adenosine diphosphate (ADP) or collagen and epinephrine inducing a platelet plug to form which closes the aperture.

The PFA test result is dependent on platelet function, plasma von Willebrand Factor level, platelet number, and (to some extent) the hematocrit. The PFA test is initially performed with the Collagen/Epinepherine membrane. A normal Col/Epi closure time (<180 seconds) excludes the presence of a significant platelet function defect. If the Col/Epi closure time is prolonged (>180 seconds), the Col/ADP test is automatically performed. If the Col/ADP result is normal (<120 seconds), aspirin-induced platelet dysfunction is most likely. Prolongation of both test results (Col/Epi >180 seconds, Col/ADP >120 seconds) may indicate the following;