Related Experiment Video
Updated: Jan 24, 2026
10:24
Morris Water Maze Test: Optimization for Mouse Strain and Testing Environment
Published on: June 22, 2015
22.4K
Clozapine and N-Desmethylclozapine (Norclozapine) Proficiency Testing Data, 2012-2024
Lewis Couchman1, Karen Morgan2, Susanna Every-Palmer3
1Analytical Services International Ltd, St. George's-University of London, London, United Kingdom.
Therapeutic Drug Monitoring
|January 23, 2026
Summary
Serum clozapine proficiency testing shows increased liquid chromatography-mass spectrometry use did not improve analytical performance. Method validation should address potential interferences and unexpected results require repeat analysis.
Area of Science:
- Clinical Chemistry
- Pharmacology
- Analytical Chemistry
Background:
- Proficiency testing schemes are crucial for monitoring laboratory performance in therapeutic drug monitoring.
- Clozapine and norclozapine are essential antipsychotic medications requiring accurate quantification.
- Assessing analytical methods used in clozapine and norclozapine testing is vital for patient safety.
Purpose of the Study:
- To summarize data from a serum clozapine and norclozapine proficiency testing scheme.
- To evaluate the impact of analytical methods on quantitative performance over time.
- To identify potential issues in clozapine and norclozapine measurement.
Main Methods:
- Analysis of monthly returns from a clozapine and norclozapine proficiency testing scheme (2012-2024).
- Tracking the proportion of laboratories using different analytical techniques, including liquid chromatography-mass spectrometry (LC-MS) and high-performance liquid chromatography (HPLC).
- Assessment of quantitative performance using z-scores and analysis of reported clozapine and norclozapine concentrations.
Main Results:
- 191 laboratories participated, with 164 reporting norclozapine results.
- The use of LC-MS increased to 74% by 2024, while HPLC use decreased.
- Detectable clozapine concentrations were reported in 6.8% of returns, with some high concentrations reported as "0" or below the limit of quantification.
- No significant temporal differences in quantitative performance (z-scores) were observed between analytical methods.
- Median clozapine z-scores were further from zero when clozapine alone was measured compared to when both clozapine and norclozapine were measured.
Conclusions:
- Increased adoption of LC-MS did not correlate with improved analytical performance for clozapine or norclozapine.
- Method validation should incorporate assessment of interference from metabolites and co-administered drugs.
- Unexpected quantitative results necessitate repeat analysis or, when feasible, repeat sampling for clinical confirmation.
Related Concept Videos
01:16Statistical Inference Techniques in Hypothesis Testing: Parametric Versus Nonparametric Data
463
Statistical inference techniques, paramount in hypothesis testing, differentiate into two broad categories: parametric and nonparametric statistics.
Parametric statistics, as the name suggests, assumes that data follow a specific distribution, often a normal distribution. This assumption enables robust hypothesis testing and estimation. Parametric methods, like the Student's t-test or Goodness-of-fit test, are frequently employed in biostatistics due to their robustness. For instance,...
Parametric statistics, as the name suggests, assumes that data follow a specific distribution, often a normal distribution. This assumption enables robust hypothesis testing and estimation. Parametric methods, like the Student's t-test or Goodness-of-fit test, are frequently employed in biostatistics due to their robustness. For instance,...
463
00:59How Data are Classified: Numerical Data
37.0K
Data that are countable or measurable in specific units are called numerical or quantitative data. Quantitative data are always numbers. Quantitative data are the result of counting or measuring the attributes of a population. Amount of money, pulse rate, weight, number of people living in a town, and number of students who opt for statistics are examples of quantitative data.
Quantitative data may be either discrete or continuous. All quantitative data that take on only specific numerical...
Quantitative data may be either discrete or continuous. All quantitative data that take on only specific numerical...
37.0K
01:11How Data are Classified: Categorical Data
43.1K
A variable, usually notated by capital letters such as X and Y, is a characteristic or measurement that can be determined for each member of a population. Data are the actual values of variables. They may be numbers, or they may be words. Datum is a single value.
Data are classified based on whether they are measurable or not. Categorical data cannot be measured; instead, it can be divided into categories. For example, if Y denotes a person's party affiliation, some examples of Y include...
Data are classified based on whether they are measurable or not. Categorical data cannot be measured; instead, it can be divided into categories. For example, if Y denotes a person's party affiliation, some examples of Y include...
43.1K
01:24Data Reporting and Recording
5.4K
Reporting and recording are crucial in data documentation. The timely, thorough, and accurate documentation of facts is essential when recording patient data. Failure to record findings during an assessment or interpretation of a problem will result in loss of information and make the patient document unreliable. The reader is left with general impressions if the information is not specific. A recording is documenting data of the individual's health information in a traceable, secure, and...
5.4K
01:30Data Collection I
7.9K
Data collection gathers information needed to make accurate judgments about a patient's present condition. During a health history interview, subjective data is collected from the patient, their caregivers, or family members, and objective data is collected through observations and physical assessment. Patients are the primary source of subjective data. Thus information gathered from patients through interviews, observations, and physical examination is primary data. Secondary sources of...
7.9K
01:03Data Validation
6.4K
Data validation is an essential part of a comprehensive assessment. Validation is confirming or verifying and opening the door to gathering more assessment data as it clarifies vague or unclear data. The process of checking and verifying the collected information is called data validation. The primary purpose of data validation is to ensure data is as free from error, bias, and misinterpretation as possible.
Nursing assessment guides are generally based on holistic models rather than medical...
Nursing assessment guides are generally based on holistic models rather than medical...
6.4K