**6.2 Clinical data**

There are hopefully much more clinical studies comparing 99Tc-DTPA with other markers. After the preliminary study published by Hauser (Hauser et al., 1970), the performances of 99Tc-DTPA clearance was studied from the seventies. Klopper may be considered as one of the pioneers with this markers (Klopper et al., 1972). The first studies were however comparing 99Tc-DTPA with iothalamate and the samples were limited (Table 6)(Klopper et al., 1972; Rootwelt et al., 1980). The first study comparing 99Tc-DTPA with inulin was published in 1984 (Rehling et al., 1984). In table 3, we resumed the results of studies comparing 99Tc-DTPA with the gold standard method in adults. Two studies have compared with good statistical methods the urinary clearance of 99Tc-DTPA and inulin. In the study published by Lewis in 1989, the bias was excellent bias (near to 0) but the precision was not satisfying (± 18 mL/min)(Lewis et al., 1989). One year later, Perrone showed excellent concordance between urinary clearances of 99Tc-DTPA and inulin in 13 chronic kidney disease (CKD) patients. However, the results were less impressive in the 4 healthy subject where 99Tc-DTPA clearances overestimate (+12 mL/min) inulin clearances. Definitive conclusion about the performance of 99Tc-DTPA plasmatic clearance is difficult to draw and we clearly need additional studies on this topic.
