Diagnostic Stewardship as a Model To Improve the Quality and Safety of Diagnosis

Diagnostic errors include missed, delayed, and wrong diagnosis, as well as failure to communicate the diagnosis effectively to the patient and family members.²⁰ Interventions to improve diagnostic testing should target breakdowns in the testing process that lead to diagnostic error. 

The total testing process (Figure 1) is a model that can help identify and classify failure points in the process of test ordering, collection, processing, and reporting.¹⁵ 

Figure 1. The total testing process

Source: Lubin IM, Astles JR, Bunn JD, et al. The clinical laboratory is an integral component to health care delivery: an expanded representation of the total testing process. Am J Clin Pathol 2023 Aug 1;160(2):124-129. https://doi.org/10.1093/ajcp/aqad038.

While the model outlines a complex process with multiple structural and systemic components, a simpler way to conceptualize diagnostic errors in the testing process is to classify them as preanalytic, analytic, or postanalytic^10,11:

• Preanalytic errors refer to problems with test selection, ordering, and specimen collection.¹⁰ Often, such errors reflect ordering diagnostic tests in the setting of low pretest probability of a disease, increasing the likelihood of a false positive or overdiagnosis. A well-known example is ordering urine cultures in patients without urinary tract symptoms, which can increase the risk of wrong (false positive) diagnosis of urinary tract infections and lead to inappropriate use of antibiotics.²⁶ 
  
  Underuse of diagnostic tests is also frequently implicated in diagnostic error^27,28 but is less often discussed in the context of diagnostic stewardship. Preanalytic errors may also result from specimen mishandling; for instance, contamination of specimens at the time of collection can result in wrong diagnosis and unnecessary treatment.^10,29,30 Blood cultures are an area of special concern given high rates of use and high rates of specimen collection errors, including inadequate specimens and contamination.³⁰
• Analytic errors refer to problems performing a clinical laboratory test (usually in the laboratory setting but also applicable to point-of-care testing). These errors can occur through inappropriate or inadequate quality control procedures, atypical characteristics of the test specimen, and presence of substances that interfere with analysis.^31,32 Interpretive errors can lead to misdiagnosis; for example, in a study of second-opinion pathology reviews, 6 percent of cases had major discrepancies with potential to affect patient care.³³
• Postanalytic errors include problems with interpretation, reporting (e.g., ambiguity about diagnosis or necessary next steps in the workup), and use of test results to inform diagnoses. While the failure to correctly interpret a diagnostic test result may reflect knowledge gaps or cognitive error, the problem of postanalytic errors could be structure or process related. 
  
  For instance, the optimal use of next-generation sequencing in the neonatal critical care setting depends on the availability of a multidisciplinary team to assist with interpretation, relay critical information to clinicians to inform time-sensitive diagnosis, and communicate findings to the patient’s family.³⁴ If access to the appropriate expertise to interpret these complex tests is limited, the correct diagnosis could be delayed or missed.