Delta checks are quality control procedures used in laboratory information systems to compare current test results with previous results from the same donor. They are designed to detect clinically significant changes that may indicate specimen mix-ups, analytical errors, or true physiological changes requiring immediate clinical attention.

Types of Delta Checks

1. Percent Change Delta

Percent change delta calculates the difference between current and previous results as a percentage of the previous result. This method is particularly useful for analytes whose acceptable variation is proportional to their concentration levels.

Formula: $\% \Delta = \frac{{V_{new} - V_{old}}}{{V_{old}}} \times 100$

2. Absolute Change Delta

Absolute change delta measures the simple arithmetic difference between current and previous results, expressed in the units of measurement. This approach is beneficial for analytes where the clinically significant change is independent of the baseline value.

Formula: $\Delta = V_{new} - V_{old}$

Configuring delta checks

Delta checks can be configured in the test result spec admin page.

When a delta check is triggered, bLIS will flag the result for review by placing a red badge next to the result. This is to help prevent the release of potentially erroneous results.

Considerations

• It is recommended that both percent change and absolute change thresholds are configured. This is due to a limitation in calculating percent change, where if the previous result is 0, the formula will fail because we cannot divide by zero.
• If both percent change and absolute change thresholds are configured, percent change will take precedence. In this scenario, absolute change will only be evaluated if the percent change does not pass the configured threshold.