A medical worker conducts a paternity test in Guangzhou, Guangdong province, in this photo taken in August 2004. [China Daily]

The ongoing national census has triggered a surge in DNA paternity tests in Guangzhou.

The tests are a prerequisite for getting a hukou, or household registration, for those without birth certificates.

Southern Medical University did 260 tests for obtaining a hukou and 70 for other purposes in October alone, said Tai Yunchun, a lecturer with the judicial appraisal center at the university.

The center usually does about 70 such tests a month, he said.

"People have been lining up to take a test and we have to work extra hours," Tai said.

The center charges 1,500 yuan ($224) for a test.

The sixth national census started in the world's most populous country on Nov 1, with everyone required to provide information.

To receive a hukou, an applicant is normally required to hand in his or her birth certificate.

But thanks to the census, anyone without a birth certificate is allowed to apply for a hukou and anyone born contrary to the family planning policy will receive a lower-than-usual fine.

Some applicants did not get birth certificates because their births violated the family planning policy, while others either lost theirs or did not have one due to home delivery or adoption.

The Third Affiliated Hospital of Guangzhou Medical University did 111 paternity tests in October, more than 90 percent for a hukou, said Li Qing, a doctor with the judicial appraisal institute of the hospital.

The hospital conducted 549 paternity tests in the first 10 months of this year, up from 300 last year.

People from other cities including Shenzhen, Zhuhai and Dongguan in Guangdong have also come to take tests.

Although only five institutes in Guangzhou are designated by authorities for hukou-related paternity tests, some websites have been actively promoting their paternity test services, with one online ad offering a fee of 2,480 yuan for a single parent.