The invention relates to a method for detecting residual, undifferentiated pluripotent stem cells (PSCs) in a culture of cells differentiated from PSCs, the method comprising: culturing the cells on a substrate coated with laminin-521 and E-cadherin in a medium comprising a ROCK inhibitor; quantitating in the cultured cells expression of a marker of residual, undifferentiated PSCs; and comparing the marker expression in the cultured cells with the marker expression in a reference culture of cells comprising a known proportion of PSCs, wherein lower marker expression in the culture of cells than marker expression in the reference culture of cells indicates absence of residual, undifferentiated PSCs in the cultured cells or presence of residual, undifferentiated PSCs in the cultured cells at a proportion lower than the known proportion of PSCs in the reference culture of cells. The invention also relates to a method for manufacturing a therapeutic composition and a method for treating or preventing a condition in a subject.