Table 1.

Most accurate cutoff to discriminate between MM and MGUS cases based on the absolute number of PB circulating tumor PC

Variable	No. of CTPC/μL of PB
Cutoff value	0.058 CTPC/μL
Sensitivity	80%
Specificity	80%
AUC	88%
Positive predictive value (%)	65%
Negative predictive value (%)	90%
No. of MGUS cases below cutoff/total (%)	120/150 (80%)**
No. of MM cases above cutoff/total (%)	55/68 (81%)
False-positive cases (%)	30/150 (20%)
False-negative cases (%)	13/68 (19%)

PB peripheral blood, PC plasma cell, CTPC circulating tumor PC, MGUS monoclonal gammopathy of undetermined significance, MM symptomatic multiple myeloma, AUC area under the curve, No. number.

*p <0.0001. **6/30 (20%) MGUS cases above the cutoff have progressed to MM after a median follow-up of 17 months