Using this test, a positive diagnosis is made when antibody levels in a blood sample taken late in illness are at least four times higher than those found in a sample taken early in illness.

利用这一试验，在疾病晚期所采血液样本中抗体水平比疾病初期所采样本中发现的抗体水平至少高4倍时作出确定的诊断。

youdao

It can take up to four working days to test a single sample at a laboratory.

BBC: Wales

The majority of the sample was able to perform as high as level four (out of five) of the literacy test, meaning they were able to read, comprehend and answer questions about a simple text, and level three in numeracy, i.e. they were able to perform basic arithmetic operations.

UNESCO: Country Profile: Angola