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Abstract: SA-PO616

Probability of Target Attainment Estimated by Residual Blood Sampling Agrees with Intensive Sampling Predictions

Session Information

  • Pharmacology
    October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
    Abstract Time: 10:00 AM - 12:00 PM

Category: Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)

  • 1700 Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)


  • Giordano McAuliffe, Christin M., Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Akers, Katherine, Western Nephrology, Denver, Colorado, United States
  • Salani, Megha, Nephrology Associates of Mobile, PA, Mobile, Alabama, United States
  • Verhoven, Sylvia M., Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Patel, Pratish C., Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Colby, Jennifer M., Vanderbilt University Medical Center, Nashville, Tennessee, United States
  • Shotwell, Matthew S., Vanderbilt University, Nashville, Tennessee, United States
  • Fissell, William Henry, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Patients with critical illness and multiple organ failure have altered pharmacokinetics and are at risk of over- or under- dosing. Patient-specific estimates of target attainment require timed and repeated phlebotomy. This additional loss of blood is undesirable and, in a research setting, requires individual informed consent. Blood tests ordered for clinical purposes rarely consume the entire sample volume. We hypothesized that residual blood samples could be used to estimate target attainment in critically ill patients.


We adapted Bayesian population-pharmacokinetic statistical tools to accommodate the sparse sampling and irregular timing of clinical samples. This method incorporates dosing history, a priori estimates of population heterogeneity, other available clinical information, and patient-specific measurements of piperacillin concentration in residual blood samples to estimate patient-specific probability of target attainment. We compared these estimates to a gold-standard estimate of target attainment using intensive repeated sampling in ten patients.


There was excellent agreement between the two methods. Just one of ten subjects was misclassified as having failed to meet target exposure, and that was in a subject whose residual sample was obtained 72 hours prior to intensive sampling for the gold-standard estimate. Excluding this subject, the correlation between the residual and gold-standard estimate of drug exposure was 0.91 (95% CI: 0.62, 0.98). No subjects were misclassified as having attained target exposures when they had not.


Although this was a small sample, consistent results in this subtype of patient demonstrates that residual blood sampling may be useful for the estimation of antibiotic target attainment. As a result, residual blood sampling may be an efficient use of patient blood, a scarce resource, for pharmacokinetic measurements and therapeutic drug monitoring. Overall, residual blood sampling would reduce blood loss and potentially lower requirements for blood transfusion during a prolonged hospital stay. In addition, use of residual blood sampling may increase research participation, as it would allow for the avoidance of additional venipuncture which is often a common barrier to consent.


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