Review Article
Cytologic-Histologic Correlation Stephen S. Raab, MD1 and Dana M. Grzybicki, MD2
The process of cytologic-histologic correlation is highly valuable to the fields of both cytopathology and surgical pathology, because correlation provides a wealth of data that may be used to improve diagnostic testing and screening processes. In this study, overall improvement appeared to be driven largely by improvement in preanalytic Papanicolaou (Pap) test sampling, because longer institutional participation also was associated with improved sampling sensitivity. The authors hypothesized that Pap test sampling may have improved secondary to the introduction of liquid-based technology, which was implemented in many laboratories during the study time frame. Through the performance of continuous data tracking and retrospective root cause analysis to identify factors that may have influenced any observed changes in performance indicators, institutions may learn which initiatives are successful or unsuccessful. The future of correlation lies in the standardization of methods, the development of more formal and rigorous root cause analysis processes to determine system components underlying correlation discrepancies, and the active use of correlation data to redesign testing and screening processes for quality and patient safety improveC 2011 American Cancer Society. ment. Cancer (Cancer Cytopathol) 2011;119:293–309. V KEY WORDS: cytopathology, correlation, medical error, quality assurance, quality improvement.
Cytologic -histologic (CH) correlation is a method of medical error detection1 that is used most frequently by cytopathology personnel to evaluate failures in cytologic screening or diagnostic tests. Simply put, CH correlation is the process by which cytologic and histologic interpretations are compared, generally from the same anatomic site, to determine whether they are concordant or discordant.2-9 In most scenarios, a discordant diagnosis meets the Institute of Medicine (IOM) definition of medical error.1 In this article, we review the methods by which CH correlation is performed and the results of CH correlation root cause analysis (RCA) that determine the sources of testing and screening failures. The use of these RCA data to drive system redesign for quality improvement purposes also will is discussed. Medical Error The IOM defined a medical error as the failure of a planned action to be completed as intended or the use of a wrong plan to achieve an aim.1 This definition encompasses all types of error, including those occurring in diagnostic testing and screening, and does not link patient outcome to error. Pathology laboratories traditionally have considered 2 types of error: errors of accuracy and errors of precision.10,11,12 Accuracy is the closeness of a measure to its true value. For example, a cytologic diagnosis is accurate if that diagnosis corresponds to the Corresponding author: Stephen S. Raab, MD, Department of Pathology, University of Colorado Denver, 12605 East 16th Avenue, Anschutz Inpatient Pavilion, Room 30, Aurora, CO 80045; Fax: (303) 848-4454;
[email protected] 1
Department of Pathology, University of Colorado, Aurora, Colorado; 2Department of Specialty Medicine, Rocky Vista University, Parker, Colorado
Received: February 7, 2011; Revised: April 14, 2011; Accepted: April 13, 2011 Published online July 5, 2011 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/cncy.20165, wileyonlinelibrary.com
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Review Article
disease process in the patient. Precision is the degree to which repeated measures produce the same results; and, in screening and diagnostic testing, precision is often referred to as diagnostic reproducibility. For example, a diagnosis is precise if 2 cytopathologists independently examine the specimen slides and make the same diagnostic interpretation. A lack of reproducibility is problematic on several levels, because it may reduce trust among clinicians and pathologists and, at times, it may create uncertainty medical decision making. An error detected by CH correlation is usually an error of accuracy, although interpathologist disagreement about the cause of a correlation error is an example of an error in precision.11 Both of these error types are discussed in more detail below. Medical errors, as described in the IOM report To Err Is Human, medical errors permeate all levels of health care.1 Patient safety researchers believe that most human errors are made in faulty systems; medical errors generally happen because of active events occurring in a system with latent conditions that lead to active failures.1 A surgeon amputating the wrong leg is an example of an active error.1 Latent conditions leading to this error may include the lack of mandatory time-out checks to prevent an error13-15 or an operating room that is excessively busy. A specific concept that has an important bearing on medical error, especially errors detected by CH correlation, is the step-wise process of diagnostic testing and screening. This process has been described as the total testing process (TTP), which is a system-based framework for examining all possible interactions and activities that may affect the quality of cytologic and surgical pathology tests.16-18 For the process of CH correlation, the steps of interest occur in the preanalytic phase and the analytic phase for both tests. These 2 phases are defined by the activities that align with the clinical workflow internal and external to the laboratory as 1) the preanalytic phase (patient identification, specimen procurement, and transport) and 2) the analytic phase (specimen processing and interpretation). Errors that occur in individual steps19 may lead to an error detected by the CH correlation process.3
Methods of Error Detection Medical errors may be detected using a variety of methods, which often are described in a dichotomous manner, such as active or passive, retrospective or prospective, and 294
self-reporting or third-party reporting, to name a few.20,21 The method of detection determines the frequency and type of error and the severity of clinical outcomes associated with the error. For example, active error-detection methods, such as performing direct observations, detect a higher frequency of error than passive methods, such as reviewing charts or CH correlation diagnoses.11,22 Active methods seek out errors in progress, and passive methods detect errors after they happen. CH correlation most commonly is performed in a retrospective and passive manner and through third-party reporting.2-9 Because of this process, the determination of cause may be difficult because of the general inability to evaluate all steps in the testing process to determine where failures occurred.3 Because correlation evaluates only cases in which both a cytologic and a surgical pathology specimen have been procured, the method does not evaluate the majority of either all cytologic or all surgical pathology cases and, thus, cannot provide a frequency of all cytologic or surgical pathology errors.3 Because correlation generally evaluates cytologic specimens that are antecedent or concurrent to surgical pathology specimens, the method focuses more on detecting cytologic rather than surgical pathology errors. The process of CH correlation is regulated by the Clinical Laboratory Improvement Amendments of 1988 (CLIA 1988) and is viewed as part of a laboratory’s overall quality-control program.23 The CLIA 1988 regulations stipulate that laboratories must establish and follow policies and procedures written for a program that is designed to detect errors in both the performance of cytologic examinations and the reporting of results. This program must include laboratory comparison of the available clinical information with cytology reports as well as comparison of gynecologic cytology reports of high-grade squamous intraepithelial lesion (HSIL), adenocarcinoma, or other malignant neoplasms with the histopathology report, when available in the laboratory (either on site or in storage), and a determination of the causes of any discrepancies.23 In some laboratories, CH correlation is performed on a prospective basis, often on surgical pathology specimens, before specimen sign-out, with antecedent cytology. This process is a form of quality improvement and lowers the error frequency for surgical pathology specimens.11,24,25 Cancer Cytopathology
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Cytolotic-Histologic Correlation/Raab and Grzybicki
Limitations in the Methods of CH Correlation
Table 1. Fifteen Minimal Variables for the Performance of Cytologic-Histologic Correlation
North American laboratories are not standardized in the performance of CH correlation.26 A specific method for the performance of correlation for Papanicolaou (Pap) test-histologic specimen pairs is not outlined in the CLIA 1988 regulations.23 The performance of CH correlation for nongynecologic specimens is not governmentally regulated. The lack of a nationally standardized method for the performance of CH correlation is problematic for several reasons. First, because CH correlation is performed in a nonstandard way, it is difficult, if not impossible, for laboratories to compare data.26 Second, the lack of standardization results in laboratories performing CH correlation with variable rigor, which affects error detection frequencies. Because errors often have a negative connotation, a bias exists to not perform correlation in a manner to detect error.26-29 Third, the lack of correlation guidelines does not allow for laboratories to employ ‘‘best practices’’ to use correlation data for self-improvement.30 The ability to perform CH correlation depends on the laboratory information system. Electronic laboratory information systems vary in their ability to track cytologic and histologic correlation pairs.26,30,31 Vrbin et al conducted a survey of 162 American laboratories on current CH correlation practices26 to obtain evidence regarding the existing level of variability in correlation methods. The respondent laboratories sent tools that were classified into the categories of forms, logs, or tally sheets. Those authors constructed a list of variables to compare the amount of specific CH correlation information recorded by each institution. The list of variables was derived from the College of American Pathologists (CAP) Commission for Laboratory Accreditation Cytopathology Checklist and from the materials sent by the individual laboratories.32,33 On the basis of the CAP checklist, 15 items (Table 1) were considered key variables when performing CH correlation, and Vrbin et al classified these variables as the minimum expected set of variables that could be collected. The response rate was 32.1% (52 laboratories responded), and a total of 84 CH correlation tools were obtained.26 The only minimum expected variables listed by >50% of laboratories were cytology case number, signout cytology diagnosis, surgical pathology case number,
1. Cytology case number 2. Sign-out cytology diagnosis 3. Sign-out cytologist 4. Original cytotechnologist diagnosis (for gynecologic cases) 5. Sign-out cytotechnologist (for gynecologic cases) 6. Review cytology diagnosis 7. Review cytologist 8. Surgical pathology case number 9. Sign-out surgical pathology diagnosis 10. Sign-out surgical pathologist 11. Review surgical pathology diagnosis 12. Review surgical pathologist 13. Significance of discrepancy (ie, effect on patient care or presumed impact on patient care) 14. Action taken (ie, what occurred as a result of identification of the discrepancy) 15. Reason for correlation (ie, if correlation was part of normal cytologic-histologic correlation, as a result of clinician concern, etc)
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and sign-out surgical pathology diagnosis. No laboratory listed all 15 of the minimum expected variables, and the majority of laboratories recorded data on
