HPRT1 and neoplasm: Furthermore, separation of patients in two groups with tumours expressing undetectable levels (<0.001 ag Hiwi mRNA per fg HPRT mRNA) or detectable levels of Hiwi transcripts (⩾0.001 ag Hiwi mRNA per fg HPRT mRNA) did not show an impact of Hiwi expression on survival (RR=1.401; P=0.328).