The newborn blood spot test is so controversial that countries that have examined the evidence have scrapped it altogether.
In a review of the screening programmes of 14 countries, including the UK and the US, researchers from the University of Warwick discovered that nearly half of the countries that still offer the test have never looked at good systematic evidence to check it is accurate, and 75 per cent haven't carried out thorough checks on the harm it can cause from over-diagnosis or false-positive readings (when the test 'sees' a problem that isn't there).
The test is offered to parents to assess whether their newborn child has any rare diseases; the number of diseases that are tested varies from country to country, and can be from just five to 60, ranging from cystic fibrosis, hypothyroidism and sickle cell disease.
Lead researcher Dr Sian Taylor-Philips commented: "This study showed that many national policy decisions about whether to screen for conditions are being made without systematically reviewing the evidence."
(Source: BMJ, 2018; 361: k1612)