Four studies (n=138 patients) were included in the review. Sample sizes ranged from 15 to 75. The duration of follow-up ranged from 2 to 71 months. The overall prevalence of clinically significant chronic tubulopathy varied from 6 to 46%.
Urinary beta 2 microglobulin: This was assessed in two studies (n=48). One study (n=23) defined abnormal urinary beta 2 microglobulin as ≥10mg/mmol of creatinine. All three patients who had elevated levels developed chronic proximal tubulopathy, whereas none of the remaining 20 patients with lower levels of beta 2 microglobulin developed the disease (sensitivity 100%, 95% CI 29 to 100; specificity 100%, 95% CI 84 to 100). The other study (n=25) defined abnormal urinary beta 2 microglobulin levels as absolute loss of ≥ 2mg/L. Two out of the four patients with elevated urinary beta 2 microglobulin levels developed chronic proximal tubulopathy, whereas no other patients developed the disease over the 18-month follow-up period (sensitivity 100%, 95% CI 40 to 100; specificity 82%, 95% CI 74 to 98).
Aminoaciduria: This was assessed in three studies (n=113). The definition of aminoaciduria varied between the studies. The tests had a sensitivity ranging from 33% to 92% and specificity ranging from 84% to 90%. The confidence intervals around these estimates were wide.