High-Level Disinfectant Test Strips & MEC Monitoring
High-level disinfectant test strips verify that a reusable HLD solution still holds its minimum effective concentration (MEC) before you put an instrument in it. The rule is simple: test before each use, and the strip must be the one validated for your specific solution — strips are matched to a named product, not to a chemistry class, so an OPA strip and a glutaraldehyde strip are not interchangeable, and neither are two glutaraldehyde strips rated at different concentrations. Buying the wrong strip is the most common and most expensive error in this category, because it produces readings that mean nothing.
What minimum effective concentration actually measures
A reusable HLD solution is diluted every time a wet instrument enters it, and the active ingredient is consumed as it works. The solution can therefore fall below the concentration required for high-level disinfection long before its stated reuse life expires. The MEC test measures the active concentration at the moment of use — not how many days are left on the label.
Per the CDC guideline for disinfection and sterilization in healthcare facilities, the concentration should be considered unsafe when the test indicates a dilution below the product's MEC, and the results of test strip monitoring should be documented. Where the strip manufacturer specifies a quality-control procedure for the strips themselves, users should follow it.
The failure everyone gets wrong: reuse life is not a guarantee
A "28-day" glutaraldehyde is not certified to work for 28 days. Twenty-eight days is the maximum reuse period; the solution can drop below MEC on day 4 in a busy endoscopy suite. The label sets a ceiling, the strip sets the actual pass/fail. A solution that fails the strip is discarded and replaced — it is never topped off with fresh concentrate, because adding solution restores volume without reliably restoring active concentration across the bath.
Three separate clocks, and you have to track all three
This is where documentation goes wrong in practice, because each of these expires independently:
- Solution reuse life — days from activation of the disinfectant, typically 14 or 28 depending on the product.
- Strip bottle open-life — days from the date you first opened the strip bottle. This is printed on the bottle and varies by product: the MetriCide OPA Plus indicator specifies use within 90 days of opening, the Wavicide-01 indicator within 120 days, and the McKesson OPA/28 indicator carries a 6-month life from opening against an 18-month unopened shelf life.
- Strip unopened shelf life — the expiry printed for stock that has never been opened.
CDC guidance is to date the bottle of strips when it is opened and use it only for the period indicated on that bottle. Most bottles are printed with a "date opened" field for exactly this reason — write on it. An in-date, unopened-looking bottle that was actually opened five months ago will still change color and still tell you nothing.
Matching the strip to your solution
Every strip below names the exact disinfectant it validates. Match on that name and manufacturer number, not on the chemistry alone.
| Test strip | Chemistry / MEC | Strips | Validated for | McKesson # | MPN |
|---|---|---|---|---|---|
| MetriTest 1.8% | Glutaraldehyde, 1.8% | 60 | MetriCide 28 (10-2800, 10-2805); MetriCide Plus 30 (10-3200); McKesson 28-Day Glutaraldehyde (68-102800) — 28-day use life | 459974 | 10-304 |
| MetriTest 1.5% | Glutaraldehyde, 1.5% | 60 | MetriCide — 14-day use life | 459973 | 10-303 |
| MetriCide OPA Plus indicator | OPA (ortho-phthalaldehyde) | 60 | MetriCide OPA Plus (10-6000) | 1258326 | 10-602A |
| McKesson OPA concentration indicator | OPA | 50 | McKesson OPA/28 (73-OPA28) | 852218 | 73-OPA28B |
| Rapicide OPA/28 test strips | OPA | 50 | Rapicide OPA/28 (ML02-0127) | 835024 | ML02-0137 |
| Revital-Ox RESERT R60 test strip | Hydrogen peroxide (MRC) | 60 | Revital-Ox RESERT HLD (4455N9, 4455AW) | 995041 | PCC054 |
| Wavicide-01 MEC indicator | Glutaraldehyde | 40 | Wavicide-01 | 1183106 | 0306-STRIPS_IBT |
Two glutaraldehyde strips that are not substitutes
MetriTest 1.8% and MetriTest 1.5% look nearly identical on the shelf and differ by one digit in the manufacturer number — 10-304 against 10-303. They read different MEC thresholds for different reuse periods: 1.8% for the 28-day solutions, 1.5% for the 14-day. Using the 1.5% strip on a 28-day solution will pass a bath that is already below the concentration that solution requires. If your department runs both, separate them physically and label the shelf.
How to run the test
Follow the strip's own instructions, since dip and read times are product-specific — both the McKesson OPA/28 and Rapicide OPA/28 indicators, for example, specify a 3-second dip with a 90-second read. In general terms:
- Confirm the strip bottle is in date and within its open-life, and that it is the strip validated for this solution.
- Dip one strip for the specified time. Do not swirl it, and do not leave it in longer than stated.
- Hold it horizontally so solution does not run across the pad and skew the reading.
- Read at the specified time against the color chart on that bottle — not against another bottle's chart.
- Record the result, date, solution lot, and operator. Discard the strip; it is single-use.
- On a fail, discard the solution. Do not top off and do not retest the same bath hoping for a pass.
Handling and disposal
MEC testing puts staff over an open bath of active disinfectant. OSHA has no permissible exposure limit for glutaraldehyde, but the ACGIH ceiling threshold limit value is 0.05 ppm and the NIOSH recommended exposure limit is 0.2 ppm — and glutaraldehyde is a strong irritant to eyes, nose, and skin that can cause sensitization. The OSHA hospital eTool on glutaraldehyde calls for well-ventilated rooms and local exhaust ventilation, keeping baths covered or under a hood where possible, and gloves impervious to glutaraldehyde such as butyl rubber, nitrile, or Viton. Our lab PPE requirements guide covers glove and face-protection selection.
Spent OPA and glutaraldehyde solutions should be neutralized before disposal — Glute-Out and Kem-Safe are the stocked neutralizers — and disposal must follow your local wastewater authority's requirements.
Shop McKesson high-level disinfectants and MEC test strips, shipped from US inventory as an authorized McKesson dealer.
Selecting the right strip
| Your solution | Strip to order |
|---|---|
| MetriCide 28 or MetriCide Plus 30 (28-day) | MetriTest 1.8% — MPN 10-304 |
| MetriCide, 14-day use life | MetriTest 1.5% — MPN 10-303 |
| MetriCide OPA Plus | MetriCide OPA Plus indicator — MPN 10-602A |
| McKesson OPA/28 | McKesson OPA concentration indicator — MPN 73-OPA28B |
| Rapicide OPA/28 | Rapicide OPA/28 test strips — MPN ML02-0137 |
| Revital-Ox RESERT hydrogen peroxide | Revital-Ox RESERT R60 test strip — MPN PCC054 |
| Wavicide-01 | Wavicide-01 MEC indicator — MPN 0306-STRIPS_IBT |
Why buy from LabSupplies.com
As an authorized McKesson dealer we stock the strips alongside the solutions they validate — MetriCide, MetriTest, Rapicide, Revital-Ox, Wavicide, and McKesson Brand — searchable by McKesson item number and manufacturer number so you can confirm the match before you order, shipped from US inventory.
Frequently asked questions
How often should high-level disinfectant be tested?
Test before each use of the solution. Concentration falls with dilution from wet instruments and with consumption of the active ingredient, so a bath that passed yesterday can fail today regardless of how many days remain in its reuse period.
Can I use any glutaraldehyde test strip with any glutaraldehyde solution?
No. Strips are validated for specific named products and read specific MEC thresholds. MetriTest 1.8% (MPN 10-304) reads the 1.8% threshold for 28-day solutions and MetriTest 1.5% (MPN 10-303) reads the 1.5% threshold for 14-day solutions — using the wrong one can pass a bath that is already below its required concentration.
What do I do if the test strip fails?
Discard the solution and replace it. Do not add fresh concentrate to bring a failing bath back up, and do not retest the same solution for a different result. Record the failure alongside your passing results.
How long are test strips good for after opening?
It is product-specific and printed on the bottle — 90 days for the MetriCide OPA Plus indicator, 120 days for the Wavicide-01 indicator, and 6 months for the McKesson OPA/28 indicator, for example. CDC guidance is to date the bottle when you open it and use it only for the period the bottle states.
Does a passing test strip mean the solution is sterile?
No. The strip confirms only that the active ingredient is at or above minimum effective concentration. It says nothing about contact time, temperature, or whether the instrument was properly cleaned first — and an instrument that is not clean cannot be reliably disinfected.
Do I need to document MEC test results?
Yes. CDC guidance is that the results of test strip monitoring should be documented. Record the date, the result, the solution lot and activation date, and the operator, and keep the log with the reprocessing records.
By the LabSupplies.com Technical Team
Monitoring a reusable HLD bath? Browse McKesson HLD solutions and MEC test strips → or review the full workflow in our instrument reprocessing kit checklist.