ORIGINAL COMPANY-CONTEXT PRACTICE
Define a diagnostic retest metric
Original practice scenario inspired by Abbott Laboratories's public business context; this is not a reported interview question or a description of its internal systems. A synthetic operations report shows an increasing retest rate. The data includes samples, test attempts, invalid attempts, and repeat orders for new samples. How would you define and investigate the metric?
Written for independent practice using company context; this is not a verified question from a company interview.
A REASONED APPROACH
Model answer.
Define the unit and reason for a retest before counting. A repeated attempt on the same sample differs from a new sample ordered later, and invalid first attempts change the interpretation of quality.
Work through it
- Create a sample-level timeline with stable identifiers, attempt ordering, and outcome categories. Separate technical reruns, confirmation workflows, and newly ordered samples.
- Choose a denominator such as eligible first attempts, then report the proportion needing a technical rerun within a fixed window. Keep unresolved samples visible.
- Stratify by instrument, site, specimen type, and time while checking changes in mix and coding. Investigate abrupt shifts against maintenance and process changes.
Tradeoffs to discuss
- A simple aggregate supports monitoring, but reason-specific metrics are more actionable. Small strata require uncertainty and careful interpretation.
Common pitfalls
- Counting every repeated row as a retest confuses duplicates with work.
- Removing invalid attempts can conceal the operational problem the metric should reveal.