Are you seeing signal shifts when switching HEp-2 substrate lots mid-protocol? We’re supporting an autoimmune trial and reflexing ENA on positives; after a kit lot change last week, our 1:80 cutoff is catching more borderline patterns, despite identical QC (two controls, same microscope and incubator). Looking for practical tweaks (diluent, incubation time, reading rules) you’ve used to keep consistency without revalidating the whole algorithm.
despite identical QC (two controls, same microscope and incubator). Ugh, same here — two controls didn’t flag the lot shift; we fixed it by capping incubation at 25 min and adding 2‑min PBS‑Tween (0.05%) wash soaks, which pushed most 1:80 borderlines back below cutoff. If you’re still seeing speckle, try the kit’s sample diluent/mountant instead of lab PBS — did that help on your scope?
My take: I’d lean toward the simplest next step and see if it changes anything this week — if not, you’ve got a clear case to escalate. What would block you from trying that?
Quick fix that’s helped me: on lot changes I switch the wash to PBS‑T 0.05% and enforce a “90‑second final wash + 30‑second blot” before mounting; it consistently trims the weak speckly 1:80s without losing true positives. If the shift hangs on, check the diluent pH (aim about 7.4) — tiny drift matters; @Jae have you tried PBS‑T yet?
Tempting to drop to 4% for FY26, but I’d keep approvals at last year’s rate and treat the ‘cheaper debt’ as an O&M reserve — 0.5–1.0% of replacement cost per year and a mid‑life overhaul in year 7 — so the $0.6M flips still earn their k
I’d move to 4% for screening but keep approvals anchored by a +100 bps sensitivity: if NPV stays >$0 at 5%, greenlight; if not, park it… For the cheaper debt, don’t bury it in OPEX — model a scheduled mid‑life refresh as explicit capex and add a downtime penalty; that kept our “$0.6M flips” from vanishing later. @thanson1023’s reserve idea is solid, but tying release to a condition index or failure‑rate trigger has been cleaner for us.