Urgent Samples in Clinical Laboratories: Stochastic Batching to Minimize Patient Turnaround Time

Abstract

This paper addresses the problem of batching laboratory samples in hospital laboratories where samples of different priorities are received continuously with uncertain transportation times. The focus is on optimizing the control strategy for loading a centrifuge to minimize patient turnaround time (TAT). While focusing on samples of patients in life-threatening situations (i.e., vital samples), we propose several online and offline methods, including a stochastic mixed-integer quadratic programming model integrated within a discrete-event system simulation. This paper aims to enhance patient care by providing timely laboratory results through improved batching strategies. The case study, which uses real data from a university hospital, demonstrates that incorporating distributional knowledge of transport times into our decision policy can reduce the median patient TAT of vital samples by 4.9 minutes and the 0.95 quantile by 9.7 minutes, but has no significant effect on low-priority samples. In addition, we show that this is essentially an optimal result by comparison with the upper bound obtained by a perfect-knowledge offline algorithm.

Figures (13)

• Figure 2.1: Timing diagram of the laboratory process for a patient sample. The red rectangles correspond to activities whose duration is essentially deterministic, whereas the blue rectangles correspond to activities whose duration is uncertain. The light gray depicts the idle time of a sample.
• Figure 3.1: Transport time probability densities estimated by kernel density estimation of statim samples for different hospital wards.
• Figure 3.2: A fixed-schedule centrifuge policy that is not triggered by sample arrival may miss an arriving sample. The idle times of the samples are depicted in gray.
• Figure 4.1: Discrete event simulation modeling the sample transit and centrifuging in a clinical laboratory.
• Figure 4.2: Example demonstrating the unsuitable timing of the centrifuge. The centrifuge is started too early.