Tandem Queues with Impatient Customers for Blood Screening Procedures

Shaul K. Bar-Lev, Hans Blanc, Onno Boxma, Guido Janssen, David Perry

Research output: Contribution to journalArticlepeer-review


We study a blood testing procedure for detecting viruses like HIV, HBV and HCV. In this procedure, blood samples go through two screening steps. The first test is ELISA (antibody Enzyme Linked Immuno-Sorbent Assay). The portions of blood which are found not contaminated in this first phase are tested in groups through PCR (Polymerase Chain Reaction). The ELISA test is less sensitive than the PCR test and the PCR tests are considerably more expensive. We model the two test phases of blood samples as services in two queues in series; service in the second queue is in batches, as PCR tests are done in groups. The fact that blood can only be used for transfusions until a certain expiration date leads, in the tandem queue, to the feature of customer impatience. Since the first queue basically is an infinite server queue, we mainly focus on the second queue, which in its most general form is an S-server M/G[k, K]/S + G queue, with batches of sizes which are bounded by k and K. Our objective is to maximize the expected profit of the system, which is composed of the amount earned for items which pass the test (and before their patience runs out), minus costs. This is done by an appropriate choice of the decision variables, namely, the batch sizes and the number of servers at the second service station. As will be seen, even the simplest version of the batch queue, the M/M[k, K]/1 + M queue, already gives rise to serious analytical complications for any batch size larger than 1. These complications are discussed in detail, and handled for K = 2. In view of the fact that we aim to solve realistic optimization problems for blood screening procedures, these analytical complications force us to take recourse to either a numerical approach or approximations. We present a numerical solution for the queue length distribution in the M/M[k, K]/S + M queue and then formulate and solve several optimization problems. The power-series algorithm, which is a numerical-analytic method, is also discussed.

Original languageEnglish
Pages (from-to)423-451
Number of pages29
JournalMethodology and Computing in Applied Probability
Issue number2
StatePublished - Jun 2013

Bibliographical note

Funding Information:
Acknowledgements We are grateful for the constructive comments and questions of the referee, which led to a significant improvement of the paper. The research of Shaul Bar-Lev and David Perry was supported by a visitor grant from the Netherlands Organisation for Scientific Research NWO.


  • Blood screening procedures
  • Group testing procedures
  • Impatient customers
  • Tandem queues

ASJC Scopus subject areas

  • Statistics and Probability
  • General Mathematics

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