Before doctors carried out a rare life-saving bone marrow transplant on cancer sufferer Arna Buckley, they ordered DNA tests to make sure her twin was indeed identical.
It's tempting to say they needn't have bothered - the sisters are so alike that staff at Waikato Hospital mixed up the two during Mrs Buckley's treatment for lymphoma and leukaemia last year.
"Because I lost my hair, she shaved her head," says Mrs Buckley of her twin sister, Luana Tupou.
"I'd be in the shower and Luana would lie down on the bed for a rest, and the nurses would come in and they'd be about to treat her."
Mrs Buckley, 39, now calls Ms Tupou "my life-saver" after she received a syngeneic bone marrow transfer - possible only for those with an identical twin - which saved her life after chemotherapy failed.
Bone marrow transplants can lead to the sometimes fatal "graft versus host" disease, where donated cells attack normal cells. But because cells from Ms Tupou were a perfect match there was little risk.
"It's a blessing that I did have an identical twin ... she said she'd do anything to help me. She said it was an honour to be my donor. She was just awesome," Mrs Buckley said.
Now in remission, the Papamoa mother of two is back at work and her hair has regrown a little.
On March 28 she and Ms Tupou will shave off their hair in support of Leukaemia and Blood Cancer New Zealand's Shave for a Cure fundraising campaign. Shave for a Cure Week runs from March 26-30 and last year 4000 New Zealanders took part.
Mrs Buckley says it's an opportunity to give something back after the foundation helped her family out with petrol vouchers - "every little bit helps" -and other support during her illness.
Mrs Buckley found a lump on her chin in December 2010. Her doctor diagnosed it as a saliva stone stuck in a duct and prescribed antibiotics, and staff at an A&E clinic later believed her symptoms to be caused by a viral infection. She continued to suffer from tiredness, numbness and night sweats, and when excruciating pains shot down both arms she was taken to Waikato Hospital. On January 6 last year doctors told her she had two cancers - leukaemia and lymphoma.
When three cycles of chemotherapy failed to make progress the sisters underwent the marrow transfer.
"I started to come right. My energy levels started to go up. And I started work on September 1," Mrs Buckley says. She credits her faith and the unhesitating support of friends and family for helping her get through.
"There were only two nights [out of four months] that I stayed in Ward 25 that I didn't have someone stay with me ..."
Ms Tupou now works as an orderly at Waikato Hospital. She started the job while her twin was being treated.
"Every break I had, she'd come visit me. If she knew I had to go somewhere for tests, she'd always be there as my orderly to take me."