QC Limits

QConnect Limits provide users robust, pre-determined control limits. Traditional QC approaches used to determine QC limits have been derived or modified from clinical chemistry and may not be applicable to serology or NAT. QConnect Limits, developed by NRL1, utilise historical data to determine expected upper and lower values of results for each QC sample/assay combination. These statistically validated QConnect limits flags when your system is not running to specification.

1.Dimech W, Vincini G, Karakaltsas M. Determination of quality control limits for serological infectious disease testing using historical data. Clin Chem Lab Med. 2014 Aug 12.

All QConnect participants using the same QC sample/assay combination submit results to EDCNet. Over time, multiple lots of QC samples tested by many laboratories, operators and instruments across numerous lots of reagents are collected. These results reflect the expected variation for that QC sample/assay combination and is  used to determine an upper and lower limit for each QC sample/ assay combination. These limits allows for the identification of unacceptable variation.  QConnect ranges aid in investigation of the source of variation including reagent lot numbers; instruments or equipment calibration and maintenance; operator errors; assay and QC sample storage and transport or environmental conditions.

Download: QConnect Limits Overview

How to use QConnect Limits

When entering data into EDCNet, results outside the QConnect Limits for that QC sample/assay combination are flagged in red indicating further investigation is required. All results outside the QConnect Limits are held in quarantine until they are validated by an NRL staff member. Participants can overlay the QConnect Limits on Levey-Jennings and other EDCNet charts in conjunction with laboratory-specific and peer group limits. NRL also provides a suggested approach, including a check list, for the investigation and troubleshooting of unexpected results.

Note: QConnect QC samples are used in addition to the manufacturers’ controls and as such, the manufacturers’ instructions for validating an assay should be adhered to.

Download: Investigation of Unexpected Quality Control Results

Download: First Line Checklist