What can we really learn from home blood testing kits?

Companies selling private blood tests offer customers a way to check their health - from measuring cholesterol levels to thyroid hormones - from the comfort of their home. But what happens if there's an abnormal result? Madeleine Finlay speaks to health journalist Emma Wilkinson and consultant chemical pathologist Dr Bernie Croal about how these tests work, how to interpret your results and whether an already overstretched NHS is being left to deal with the worried well