Dot size, lead time, fallibility, and impact on survival: continuing controversies in mammography

Learning from diagnostic errors: a good way to improve education in radiology

PURPOSE

To evaluate the causes and the main categories of diagnostic errors in radiology as a method for improving education in radiology.

MATERIAL AND METHODS

A Medline search was performed using PubMed (National Library of Medicine, Bethesda, MD) for original research publications discussing errors in diagnosis with specific reference to radiology. The search strategy employed different combinations of the following terms: (1) diagnostic radiology, (2) radiological error and (3) medical negligence. This review was limited to human studies and to English-language literature. Two authors reviewed all the titles and subsequently the abstracts of 491 articles that appeared pertinent. Additional articles were identified by reviewing the reference lists of relevant papers. Finally, the full text of 75 selected articles was reviewed.

RESULTS

Several studies show that the etiology of radiological error is multi-factorial. The main category of claims against radiologists includes the misdiagnoses. Radiologic "misses" typically are one of two types: either missed fractures or missed diagnosis of cancer. The most commonly missed fractures include those in the femur, the navicular bone, and the cervical spine. The second type of "miss" is failure to diagnose cancer. Lack of appreciation of lung nodules on chest radiographs and breast lesions on mammograms are the predominant problems.

CONCLUSION

Diagnostic errors should be considered not as signs of failure, but as learning opportunities.

Spectrum of diagnostic errors in radiology

Diagnostic errors are important in all branches of medicine because they are an indication of poor patient care. Since the early 1970s, physicians have been subjected to an increasing number of medical malpractice claims. Radiology is one of the specialties most liable to claims of medical negligence. Most often, a plaintiff's complaint against a radiologist will focus on a failure to diagnose. The etiology of radiological error is multi-factorial. Errors fall into recurrent patterns. Errors arise from poor technique, failures of perception, lack of knowledge and misjudgments. The work of diagnostic radiology consists of the complete detection of all abnormalities in an imaging examination and their accurate diagnosis. Every radiologist should understand the sources of error in diagnostic radiology as well as the elements of negligence that form the basis of malpractice litigation. Error traps need to be uncovered and highlighted, in order to prevent repetition of the same mistakes. This article focuses on the spectrum of diagnostic errors in radiology, including a classification of the errors, and stresses the malpractice issues in mammography, chest radiology and obstetric sonography. Missed fractures in emergency and communication issues between radiologists and physicians are also discussed.

How does age affect baseline screening mammography performance measures? A decision model

Background

In order to promote consumer-oriented informed medical decision-making regarding screening mammography, we created a decision model to predict the age dependence of the cancer detection rate, the recall rate and the secondary performance measures (positive predictive values, total intervention rate, and positive biopsy fraction) for a baseline mammogram.

Methods

We constructed a decision tree to model the possible outcomes of a baseline screening mammogram in women ages 35 to 65. We compared the single baseline screening mammogram decision with the no screening alternative. We used the Surveillance Epidemiology and End Results national cancer database as the primary input to estimate cancer prevalence. For other probabilities, the model used population-based estimates for screening mammography accuracy and diagnostic mammography outcomes specific to baseline exams. We varied radiologist performance for screening accuracy.

Results

The cancer detection rate increases from 1.9/1000 at age 40 to 7.2/1000 at age 50 to 15.1/1000 at age 60. The recall rate remains relatively stable at 142–157/1000, which varies from 73–236/1000 at age 50 depending on radiologist performance. The positive predictive value of a screening mammogram increases from 1.3% at age 40 to 9.8% at age 60, while the positive predictive value of a diagnostic mammogram varies from 2.9% at age 40 to 19.2% at age 60. The model predicts the total intervention rate = 0.013*AGE² - 0.67*AGE + 40, or 34/1000 at age 40 to 47/1000 at age 60. Therefore, the positive biopsy (intervention) fraction varies from 6% at age 40 to 32% at age 60.

Conclusion

Breast cancer prevalence, the cancer detection rate, and all secondary screening mammography performance measures increase substantially with age.

Screening mammography, public perceptions, and medical liability

PURPOSE

To outline the most common sources of raising malpractice claims in screening mammography and to discuss the related medical litigation issues in the light of the evidence-based medicine.

METHODS AND MATERIAL

Electronic and manual search of the relevant literature.

RESULTS

The most common cause of malpractice is the delayed diagnosis of breast cancer. The plaintiff must establish that the radiologist was negligent and the delay in diagnosis caused injury to the patient. Literature shows that mammography does not always detect breast cancer, and even skilled radiologists may periodically miss malignant lesions. Also, delay in diagnosis does not always affect treatment and prognosis. Over-promotion of screening mammography has made disproportionately difficult for a defendant radiologist to prevail in a malpractice lawsuit. Thus, screening mammography is at stake, although it saves lives. The public and legal system should be educated about biological processes, medical practice, and the limitations of screening mammography.

CONCLUSION

If mammography is to survive medical litigation and continue to save lives a major reform in public perception, in the stance of the mass media, and in the ability of legal system to understand medicine is required. Physicians and medical associations have an important role to play.