. Author manuscript; available in PMC: 2021 Oct 1.

Published in final edited form as: Curr HIV/AIDS Rep. 2020 Oct;17(5):487–498. doi: 10.1007/s11904-020-00512-3

Table 1.

Antiretroviral drug concentration thresholds and interpretations.

Drug Metabolite	Threshold Concentration	Interpretation	Limitations
*Short-term metrics of adherence*
TFV urine (44,78)	1,000–1,500 ng/mL	Ingested dose in the preceding 24 hours	Recent dose only
FTC urine (45)	1,844 ng/mL	Ingested dose in the preceding 24 hours	Recent dose only
TFV plasma (42)	35 ng/mL	Ingested dose in the preceding 24 hours at steady state	Recent dose only; requires obtaining and processing venous blood; requires LC-MS/MS^*
FTC plasma (42)	49 ng/mL	Ingested dose in the preceding 24 hours at steady state	Recent dose only; requires obtaining and processing venous blood; requires LC-MS/MS^*
FTC-TP (DBS) from F/TDF (63)	0.125 pmol/3 mm punch	Ingested dose in the preceding 24 hours at steady state	Recent dose only; requires obtaining and processing venous blood; requires LC-MS/MS^*
*Long-term metrics of adherence*
TFV-DP (freshly lysed PBMC) (14)	40 fmol/10⁶ cells	2–3 doses/week on average; 90% effective concentration for MSM	Specialty test; impractical and too costly for widespread use; requires venipuncture; requires LC-MS/MS^*
TFV-DP (DBS) from TDF (62,65)	700fmol/3mm punch	≥4 doses/week on average; >90% efficacy in MSM	Cumulative dosing only; requires LC-MS/MS^*
TFV-DP (DBS) from TAF (58)	950 fmol/two 7 mm punches	≥4 doses/week on average	Cumulative dosing only; requires LC-MS/MS^*
TFV scalp hair (59,69)	0.023 ng/mg	≥4 doses/week on average	Requires LC-MS/MS^*

LC-MS/MS limitations include expense and need for proper equipment and laboratory personnel