Positive control (CONTROL +)
The standard’s wording, as the sources below reproduce it:
“Indicates a control material that is intended to verify the results in the expected positive range.”
ISO 15223-1:2021, 5.5.4 · ISO 7000-2496
What it means for you
This control contains what the test is built to detect — an antigen, an antibody or a genetic target, often from an inactivated organism — at a level the test should pick up. Run like a sample, it must come out positive: on a lateral-flow test both the control line (C) and the test line (T) appear. If it reads negative, the kit may have lost sensitivity (stored too warm or used past its use-by date, for example) or a step was done wrong, and negative results from that kit or run cannot be relied on. It checks the opposite failure to the negative control, which is why professional kits often include both.
Whether a device is right for you is a question for your pharmacist, nurse or doctor.
- What it looks like
- A rectangle split in two: the word CONTROL on the left and a plus sign in a small cell on the right.
- Where you see it
- Professional rapid-test kits, laboratory immunoassay and molecular test kits, blood-grouping reagent sets and external-control kits: on the vial or swab label and in the kit’s contents list.
- Other names
- CONTROL plus; CONTROL +; positive control; pos control; ISO 7000-2496
What it does not tell you
It does not tell you whether the material is harmless: some positive controls are made from inactivated organisms or human material, and the kit insert says how to handle and discard them. It does not give the expected line strength or value either; the insert does.
Often confused with
Indicates a control material that is intended to verify the results in the expected negative range.
More symbols in “Letters”
Batch code (LOT)ISO 15223-1:2021, 5.1.5
Catalogue number (REF)ISO 15223-1:2021, 5.1.6
Serial number (SN)ISO 15223-1:2021, 5.1.7
Authorised representative (EC REP)ISO 15223-1:2021, 5.1.2
Model number (# in a box)ISO 15223-1:2021, 5.1.10
In vitro diagnostic medical device (IVD)ISO 15223-1:2021, 5.5.1
Control (CONTROL box)ISO 15223-1:2021, 5.5.2
Medical device (MD)ISO 15223-1:2021, 5.7.7
Unique Device Identifier (UDI)ISO 15223-1:2021, 5.7.10
Rx only (prescription device)21 CFR 801.109(b)(1)
Patient number (person with #)ISO 15223-1:2021, 5.7.1Sources
ISO 15223-1 is a paid standard, so the wording above is quoted as 3 publishers’ public documents reproduce it. Each was fetched and read on the date shown:
- NE Scientific: Master Symbol Glossary (CTF-100011 Rev 01) — Shows the CONTROL box with a plus for ISO 15223-1:2021 reference no. 5.5.4 (ISO 7000-2496): “Positive control — Indicates a control material that is intended to verify the results in the expected positive range”. Checked 2026-10-16.
- Hologic: Symbols Glossary (AW-16348 Rev. 003) — Row “Positive Control — Indicates a control material that is intended to verify the results in the expected positive range.”, ISO 15223-1:2021(E) Chapter 5.5.4, ISO 7000-2496. Checked 2026-10-16.
- QuidelOrtho: QuidelOrtho Symbol Glossary — Shows the CONTROL box with a plus cell: “Positive control — Indicates a control material that is intended to verify the results in the expected positive range”, ISO 15223-1:2016 reference no. 5.5.4, ISO 7000:2014 reference no. 2496. Checked 2026-10-16.
Plain-language parts are in our own words; quotations are the sources’ wording.