The nine studies recently conducted in the United Kingdom (Fig. 2) produce a pooled CRC miss rate of 8.7% and specificity of 77.1% (i.e. identifies people without cancer who might be able to avoid further investigations, unless there are other clinical indications for a referral, such as persistent symptoms, despite having a low f-Hb); the corresponding estimates were 7.2 and 74% in the four studies that used f-Hb <4 μg/g. The gene discussed is GSTM1; the disease is colorectal carcinoma.