Mind the gap between therapeutic drug monitoring laboratories and clinicians—bridging with clinical pharmacologists’ comprehensive assessment and interview

Clinical pharmacology is a scientific discipline dedicated to understanding and optimizing the use of drugs in humans. Its primary objective is to enhance patient care by ensuring safer and more effective drug use. ¹ This field shares some curricular overlap with clinical pharmacy, as seen in the United States and other countries, ² though the educational paths diverge—clinical pharmacologists are typically medical doctors, whereas clinical pharmacists are often trained as pharmacists.

Therapeutic Drug Monitoring (TDM), as endorsed by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT), is a multidisciplinary clinical specialty focused on optimizing patient outcomes by personalizing drug dosages. ³ Effective TDM involves considering numerous variables beyond just achieving target drug concentration levels. ⁴

The precision in administering the “right dose to the right patient” combines three key factors:

1. Patient-specific factors: Age, weight, height, ⁴ liver and kidney function, genetic polymorphisms of metabolic enzymes, comorbidities, concomitant medications, and compliance.

2. Drug-specific factors: Timing of sample collection in relation to the dose, medication history including over-the-counter drugs, ⁴ pharmacokinetic properties, steady-state achievement, drug-drug interactions, adverse reaction profiles, and toxicity potential.

3. Condition-specific factors: Disease severity scales and associated side effects, the importance of adequate disease control, the effects of disease flares on health and other organs, and the specific impact of the disease or physiological state (e.g., pregnancy, ⁵ or extracorporeal therapies in critically ill patients, i.e., extracorporeal membrane oxygenation and continuous renal replacement therapy^6,7) on pharmacokinetics and pharmacodynamics of the drugs (e.g., protein binding, receptor availability, and sensitivity, effective blood volume, drug clearance).

In addition, the sample transport processing is the logistic critical factor in bridging the gap between laboratory and clinical practice. When the clinical facility and laboratory are not co-located or situated nearby, delays in transport and temperature fluctuations can negatively influence the quality of samples. This highlights the necessity of implementing robust control throughout the chain.

We integrate these important aspects through a detailed pre-sampling interview, ensuring all relevant information is gathered before blood sample collection for laboratory analysis. This process is embedded within the hospital’s informatics system, which mandates the completion of all predefined criteria before analysis, ensuring that target drug concentrations (such as trough levels) are accurately obtained and processed under optimal conditions. Integrating a clinical pharmacologist into this oversight process ensures that preanalytical variables are systematically verified and that the conditions for accurate measurement are strictly met. Post-analysis, clinical pharmacologists synthesize the data and provide a comprehensive evaluation.

A notable observation is the common error of patients inadvertently taking medication before the interview, leading to inaccuracies in sample collection timing (collection time error). Figure 1 illustrates this patient-centered approach.

Figure 1.

The patient-centered approach is one in which the attending physician sends the patient for therapeutic drug monitoring. The patient is interviewed by the clinical pharmacologist/clinical pharmacist. All important aspects are taken into account, including those related to the individual, the drug, and the disease. This is a critical step in ensuring comprehensive individual assessment. The patient is then forwarded to the clinical laboratory to proceed with the analysis and, when done, again sent to the clinical pharmacologist to write the final report. This report includes all relevant information summarized together to serve as a significant aid in the interpretation by the attending physician.

Bridging the operational gap between laboratories and clinicians through a standardized, personalized approach fosters good clinical practice and improved patient care. The critical importance of achieving steady-state drug concentrations is underscored by reports showing over 70% of errors are due to sampling before reaching steady-state, which misrepresents actual drug levels. ⁴ Adverse drug reactions and toxicities remain significant, accounting for approximately 5% of hospital admissions. ⁸

With the rapid expansion of medical knowledge, keeping clinicians up with new information is more demanding than ever in the past. Looking ahead, future directions in TDM point toward advanced technologies. The integration of biosensors capable of real-time drug concentration measurements and the use of artificial intelligence and model-informed precision dosing holds promise in tailoring drug regimens through predictive modeling based on population pharmacokinetics and patient-specific variables. ⁹ Even with ongoing technological progress, accurate result interpretation remains essential in clinical care. Clinical pharmacology continues to play a pivotal role in optimizing drug therapy through expert assessment and oversight.

A collaborative effort across specialties is crucial. The novel practice of conducting detailed patient interviews before TDM analysis exemplifies bridging the gap between laboratory and clinical environments (see Figure 1). This approach ensures a comprehensive and patient-specific strategy in TDM, aligning clinical care with individual patient needs and advancing overall treatment outcomes.