Are certain PD-L1 assays considered more accurate or reliable than others for NSCLC?

In the treatment of NSCLC, squamous or non-squamous, there are three potential checkpoint antibodies available (Nivolumab, Pembrolizumab and Atezolizumab), only one of which is tied to a companion diagnostic of PDL1 expression by IHC (Pembrolizumab) - though in both of the other antibodies, there is...