When the bleed is real but the screen is silent, the single factor has to be cornered one at a time.
Rare bleeding disorders are a few per cent of inherited coagulation defects, so the working laboratory rarely keeps every substrate on the shelf. A single-factor deficient plasma is the reagent that lets a factor assay — or a mixing study that has localised the defect — read a specific level. Technoclone supplies the deficient plasmas, native and immunodepleted, across the PT- and aPTT-based factors. We advise on which substrate suits the assay, and keep the evidence next to the claim.
A mixing study localises the defect; the deficient plasma names it.
A prolonged PT or aPTT that corrects when mixed 1:1 with normal plasma points to a factor deficiency rather than an inhibitor. The next step is a factor assay built on a plasma deficient in just that factor, so the patient sample supplies the only variable that matters.
Patient (prolonged) · 1:1 mix with normal plasma · normal control — correction signals a deficiency, not an inhibitor.
Illustrative — schematic, not data
Clot time — patient: prolonged · 1:1 mix: corrects towards normal · normal control: baseline. Correction on mixing points to a factor deficiency; failure to correct points to an inhibitor.
Rare, but not vanishingly so — and the substrate choice is doing real work.
The published record is about epidemiology and substrate behaviour rather than a kit comparison: there is no published head-to-head of these deficient plasmas against a competitor, so every product-specific claim below is the manufacturer's and is labelled as such.
Factor VII and factor XI are among the most common across the rare-bleeding-disorder population — exact shares are registry-dependent.
Illustrative — schematic, not data
FVII and FXI are the two most common rare bleeding disorders; registry-derived shares put them at roughly 39% (FVII) and 26% (FXI) of the RBD population. Exact shares are registry-dependent — in the EN-RBD registry FXI is nearer co-equal with FVII (~36% FXI). FVII has since been reappraised as far more common than registries suggest — a minimum prevalence of about 1:17,800, roughly 28× higher than the classic 1:500,000 figure (Löwing Svensson 2025, RPTH).
Registry-based prevalence under-estimates the true figure, because milder and asymptomatic cases are never referred. The recent FVII reappraisal (≥1:17,800, ~28× higher) is the clearest example of that under-counting.
Rare bleeding disorders — the inherited factor deficiencies beyond haemophilia A/B and von Willebrand disease — make up 3–5% of all inherited coagulation factor deficiencies, ranging from about 1:2,000,000 (factor II, factor XIII) to 1:500,000 (factor VII) in the classic registry estimates.
Prevalence is registry-derived and under-estimates the true population; the bands are estimates, not a single agreed figure.
As a benchmark for how much method and laboratory matter, UK NEQAS inter-laboratory CV for factor VIII runs about 10–13% by one-stage and about 12–16% by chromogenic assay — a reminder that the substrate and method are part of the result, not a backdrop to it.
FVIII is not a rare factor; it is cited only as a well-characterised yardstick for inter-laboratory variation across single-factor assays.
An immunodepleted deficient plasma has the target factor removed to <1% residual (a manufacturer specification), leaving most other factors near normal — the property that makes it a clean substrate for measuring the patient's level of that one factor. Depletion is not perfectly selective, though: for factor VIII specifically, the antibody step co-removes von Willebrand factor, which the literature links to lower measured FVIII-inhibitor titres compared with a native, vWF-containing substrate.
The published evidence supports the direction only — that immunodepletion lowers measured FVIII-inhibitor titres — and is FVIII-specific. The magnitude of that difference is a manufacturer claim and is not stated here as a number. Native versus immunodepleted is an assay-by-assay choice; immunodepleted substrate is appropriate for most activity assays, so "native is better" should not be generalised across all factors.
There is no published head-to-head study of these single-factor deficient plasmas against a competitor product. Every product-specific performance claim is the manufacturer's [MFR] and should be read as such; the peer-reviewed figures on this page are about disease epidemiology, substrate behaviour and method variation, not about one kit beating another.
The substrate, the method, and where we add judgement.
The products
Technoclone single-factor deficient plasmas span the PT-based factors (II, V, VII, X) and the aPTT-based factors (VIII, IX, XI, XII), with contact-pathway substrates (HMWK, prekallikrein) alongside. Each is available native or immunodepleted, so the substrate can be matched to the assay rather than the other way round.
The method
A factor assay dilutes the patient plasma into the matching deficient plasma and reads the clotting time against a calibration curve; the deficient plasma supplies everything except the factor under test. A 1:1 mixing study comes first when a screen is unexpectedly prolonged, to separate a deficiency (corrects) from an inhibitor (does not).
What we do
We advise on which deficient plasma to specify when the UK market does not routinely hold it, and on native versus immunodepleted for the assay in front of you, and connect you to Technoclone's direct supply. Where a modelling or computational question arises — for example reasoning about a variant's effect — that is a human-led service we offer, not a product on the shelf.
What to expect
A reply to every enquiry, usually within two working days, with the evidence held next to the claim. Manufacturer figures are labelled as such, and where another substrate, method or supplier is the better answer for your laboratory, we say so rather than sell around it.
Every figure, sourced.
- Casini A, et al. Haemophilia 2024. DOI 10.1111/hae.14986 — 10.1111/hae.14986 (FVII ~39%, FXI ~26% of the RBD population; shares registry-dependent — FXI nearer co-equal with FVII, ~36%, in the EN-RBD registry).
- Löwing Svensson L, et al. Reappraised prevalence of factor VII deficiency. RPTH 2025 — PMC12804101 (FVII ≥ 1:17,800, ~28× higher than the classic estimate).
- Peyvandi F, James P, Salomon O, Mikovic D. Rare Bleeding Disorders. Haemophilia 2014;20(Suppl 4):71-75 — PMC4673660 (RBDs 3–5% of inherited coagulation factor deficiencies; ~1:2,000,000 FII/FXIII to 1:500,000 FVII).
- Verbruggen B, et al. The type of factor VIII deficient plasma used influences the performance of the Nijmegen modification of the Bethesda assay for factor VIII inhibitors. Thromb Haemost 2001;86(6):1435-9 — PMID 11776311 (immunodepleted FVIII-deficient plasma lacks von Willebrand factor, giving lower measured FVIII-inhibitor titres — direction only).
- UK NEQAS inter-laboratory factor VIII variation — PMID 30556650 (one-stage CV ~10–13%; chromogenic CV ~12–16%).
Tell us which factor you need to corner.
Send a short note about the factor assay, the deficient plasma you are after, or the rare bleeding disorder in front of you. We will reply with how we would approach it, what it would involve, and an honest quote — usually within two working days.