TABLE 5.

Studies in liver transplant recipients’ evaluations of association between TTV load detected by in-house PCR and allograft rejection and infection, respectively

Study designa	TX period	Included patients	Endpoint; timing	Events	Main association	Limitationsb
			Rejection
Cohort91	NA	39	BX proven rejection; <12 mo post-TX	13c	TTV pre-TX–rejection	Possible selection bias; insufficient endpoint definition; multiple testing; possible model overfitting
Cohort92	2014–2017	63	BX proven rejection; <12 mo post-TX	19c	TTV pre-BX–rejection	Missing data on BX without rejection; 2 endpoints; no effect size adjustment
			Infection
Cohort92	2014–2017	63	CMV viremia/ disease; <12 mo post-TX	26d	TTV at event–CMV viremia/ disease	Two endpoints; no effect size adjustment
Cross-sectional93	1982–2016	136	BKV events; 10 y post-TX	23	TTV at event–urinary BKV	Possible selection bias; missing data on sampling; multiple testing; no effect size adjustment
Case-control82,e	2011–2016	90	CMV viremia; <4 mo post-TX	64	TTV days 0 to 10 post-TX–CMV viremia	Possible selection bias; main analysis includes KTX; multiple testing; no effect size adjustment

^aThe studies are listed according to the date of their design and online publication.

^bAll studies followed a noninterventional and single-center design.

^cThe numbers of total biopsies were not stated.

^dFive of the cases were diagnosed with CMV disease.

^eKidney and liver transplant recipients.

BKV, BK polyomavirus; BX, biopsy; CMV, cytomegalovirus; KTX, kidney transplantation; NA, not available; PCR, polymerase chain reaction; TTV, Torque Teno virus; TX, transplantation.