Same level on the label, different behaviour in the unit

Once two products both qualify as high level, choosing between them stops being a microbiology question. Both are built to cover the same broad spectrum, so what actually separates them inside a sterilisation or endoscopy unit is operational: how much work the solution takes to prepare, what the staff around the basin are exposed to, which instrument materials tolerate it, how many days the bath stays in service, and how anyone proves the bath still works.

Detro Healthcare produces two high level disinfectants under the Detrox brand that sit on opposite sides of most of those criteria. Detro OPA is built on orthophthalaldehyde. Detro PAA 2200 is built on peracetic acid. Both are declared Class II B medical devices under the 93/42 EEC directive, which is roughly where their similarity on paper ends and their difference in daily routine begins.

Five properties carry that difference, and they are worth naming before the products are compared against them:

• Preparation: whether the solution arrives usable or has to be activated before the list can start.


• Exposure: what the people working around the basin smell and breathe.


• Material compatibility: which instrument materials the chemistry can sit against without costing the institution service life.


• Solution life: how many days the bath stays in use before it is replaced.


• Verification: how the unit checks that the solution is still doing its job.

Preparation: a container you open against a solution you activate

Preparation is the first place where two products carrying the same high level disinfectant claim stop resembling each other. One of them is a bottle you open. The other is a solution the unit brings into being.

Detro OPA is supplied ready to use. Nothing is measured and nothing is combined, and the same product serves both manual use and endoscope washing and disinfection machines. For a department where reprocessing is spread across shifts, that removes a step which can be performed incorrectly.

Detro PAA 2200 works the other way round. Its solution is made up by combining a base component with an activator, so activation becomes a task with an owner, a moment and a record. That is extra handling. It also means the unit stores two components rather than one prepared bath, and the solution only begins its life when the workload calls for it.

Neither arrangement is better in the abstract. A ready to use product suits units where staff turnover makes an added preparation step a liability. A prepared solution suits units that would rather control the moment the bath starts its life, because that starting point is exactly what the solution life is counted from.

What the people around the basin are exposed to

Odour is the property staff raise first and procurement notices last. Detro Healthcare states that Detro OPA contains no harmful gas compounds and has no odour, and describes its toxicity as low enough for safe use. The manufacturer also declares that the product shows no mutagenic, embryotoxic or teratogenic effect in humans and no effect on reproduction.

The peracetic acid side answers the exposure question with a different argument. Detro PAA 2200 is formulated without aldehydes and without phenols. Orthophthalaldehyde belongs to the aldehyde family by chemistry, so an institution that has already decided to keep aldehyde chemistry out of its reprocessing room has narrowed the field before any other criterion is even applied.

One caution belongs here. A solution nobody can smell gives the room no sensory reminder that a chemical is present. Absence of odour is a comfort property and a good one, but the handling precautions that come with a product are set by its instructions for use, not by whether anyone in the room notices the bath.

Corrosion, materials and the service life of the instrument

The cost of a wrong match here is not counted in litres of solution. It is counted in instruments. A high level disinfectant sits in direct contact with expensive devices that go through the same bath again and again, so material compatibility is where a chemistry choice quietly turns into a capital expense.

Detro OPA carries corrosion inhibitors in its formulation. Their job is to keep corrosion off the instruments passing through the solution and to extend how long those instruments stay in service. Detro Healthcare states that the product is compatible with endoscope brands and that it holds a KARL STORZ endoscope approval, which is the kind of device maker confirmation a biomedical engineering team can put on file.

Detro PAA 2200 states its compatibility as a materials list rather than a brand list. It is declared for heat resistant surgical instruments, anaesthesia instruments and dental surgical instruments, and for rigid and flexible endoscopes, with plastic, silicone, glass, acrylate and rubber among the compatible materials. For a unit whose trays mix polymers with metal, a materials list answers more questions than a brand approval does. For a unit whose load is dominated by one endoscope fleet, the brand approval answers the only question anyone is asking.

Solution life is a schedule, not a specification

Detro PAA 2200 states a solution life of at least 7 days and at most 28 days, with the actual figure depending on how soiled the load is. That range is often read as vagueness. It is the opposite. It tells the unit that its renewal date is set by its own workload rather than by a single number printed on a container.

The practical consequence is that two hospitals buying the same product will not consume it at the same rate. An endoscopy unit pushing heavily soiled instruments through the bath lives near the 7 day end of the range. A dental practice reprocessing a lighter load can sit closer to 28 days. Stock levels, consumption forecasts and the renewal reminder in the unit log all follow from where the institution actually sits inside that band, and the manufacturer's instructions define how that judgement is made.

Detro OPA takes the activation date out of the equation, because there is no activation step to date. The in use window for any bath still comes from the instructions written for that specific product, which is a figure worth confirming during evaluation rather than discovering after the first month of use.

Proving the bath still works

A solution that has been in service for two weeks is not automatically the solution that went into the basin. Carry over from wet instruments, organic load and repeated cycles all pull in the same direction, and a calendar sees none of it.

Detro PAA 2200 addresses this with test strips that can be used to measure the disinfection efficiency of the solution in use. That converts an assumption into a reading, and a reading into a record. When infection control asks how the unit knew the bath was still effective on day 19, a strip result answers in a way a renewal date on a label cannot.

Where no in use test step is part of the routine, the unit leans entirely on the renewal interval and on correct handling between renewals. That is a legitimate way to work, but it puts far more weight on the discipline of the log. This is one of the few points where the two chemistries produce a genuinely different audit trail rather than a different chemical result.

Read down that table and the split is reasonably clean. A department whose load is dominated by endoscopes, whose staffing makes an added preparation step risky, and whose biomedical team wants a device maker approval on file, is being pushed towards the orthophthalaldehyde option. A department reprocessing mixed sets across several material families, that wants aldehyde free chemistry in the room and a strip reading in the log, is being pushed towards the peracetic acid option.

Institutions that run both kinds of load sometimes carry both products, which is a defensible answer rather than an indecisive one. The two are not really competing for the same basin. They are competing for different parts of the same department.

Ranking the trade-offs is as far as an article can take this. The product that fills a given basin and the time an instrument spends submerged in it are settled by the instructions for use the manufacturer issues for that product and by whatever the institution's own infection control policy requires. A comparison narrows the field, and the protocol is written somewhere else.

Questions that come up after the shortlist

Is an odourless disinfectant automatically the safer choice for staff

It is a more comfortable one, which is not the same claim. Odour is a perception cue, and a chemistry that produces none simply gives the room no sensory signal either way. What a product does to the people handling it is described in its own documentation, and the precautions that come with it apply whether or not anyone notices it is there. Comfort is still a real procurement argument, because staff work more consistently with a product they are not trying to get away from. It should just be argued as comfort.

Does a shared Class II B declaration make two products interchangeable

No. The class describes the regulatory route the device took, not the way it behaves against a particular instrument tray. Two products can carry the same declaration under 93/42 EEC and still differ on preparation, material compatibility, solution life and the way efficiency is verified, and those four properties are what a reprocessing routine is actually built on. The class is a gate the product has to pass, not a specification the unit can plan around.