Body Vision Medical is a medical device company that offers FDA cleared LungVision solution for the effective and timely diagnosis of early-stage lung cancer in minimally invasive ways. Effective diagnosis is a key factor to improving the life expectancy of lung cancer patients.
Diagnostic yield is one of the main factors in evaluating the clinical effectiveness of an interventional medical technique, such as diagnostic bronchoscopy, intended for biopsy of suspicious lesions.
The purpose of the diagnostic yield value is to determine the probability that the selected medical technique will provide the information needed to establish a definitive diagnosis.
As most lung cancers are diagnosed at an advanced stage with very low survival rates, it is very important to achieve a definitive diagnosis at an early stage in order to increase the chances of a successful treatment. (1)
Two related questions are asked here: What would be considered a definitive diagnosis? And how is diagnostic yield calculated?
Review of the literature has demonstrated that the answer to the first question is not consistent. While some physicians consider malignant cells or a benign lesion with a follow-up as a definite diagnosis (2), other physicians refer to benign pathological abnormalities, such as tuberculosis, hamartoma, or aspergillosis, as a definite diagnosis. (3)
Since the goal is to reach a definitive decision on the nature and type of lesion that will dictate next steps in a patient’s medical treatment, the debate arises when a non-malignant result from the biopsy is received. The most accurate and conservative approach for non-malignant results would be to accommodate a 24-month follow-up period to confirm or dismiss malignancy. (4) However, a recent publication by the Fleischner Society has indicated that a shorter follow-up period might be more appropriate for selected subjects, depending on risk factors, nodule type, nodule morphology, and accuracy of measurements, suggesting that a follow up period of 12-18 months would be sufficient. (5)
The biopsy results can be classified into two categories: positive results, including malignant or benign lesions confirmed by a follow-up period, or negative results, including (1) intermediate histological samples, such as chronic inflammation, organizing pneumonia, or atypical cells without sufficient features to ascertain malignancy; or (2) indeterminate samples, such as normal lung tissue or insufficient sample size. (6) The tissue samples that produce intermediate and indeterminate samples should be further evaluated according to recommended guidelines for the management of pulmonary nodules.
The diagnostic yield of the medical technique should be defined as the proportion of patients in whom the medical technique yielded a definitive diagnosis out of the total number of patients that have received the diagnostic procedure. This value is affected by the lesions’ sizes, locations, and the existence of a bronchos sign or an airway leading directly into the lesion. (7)
The diagnostic yield is largely dependent on the diagnostic accuracy of each technique. This can be further evaluated by breaking things down into the different components within a technique, such as the chosen device for a given technique, e.g. the type of guidance device, the tools used, the biopsy instruments and the pathology analysis tools. In a study that retrospectively assessed 207 consecutive patients for the overall sensitivity of non-guided bronchoscopy compared to other modalities, for instance, it was shown that the diagnostic yield of non-guided bronchoscopy was approximately 25.6%. (8) The AQuIRE study, however, showed that in comparison, non-guided bronchoscopy combined with R-EBUS and ENB increases the diagnostic yield to 47.1% relative to non-guided bronchoscopy alone. The AQuIRE study further compared the diagnostic yield of biopsy tools and showed that Transbronchial Needle Aspirationwas diagnostic in 47.4% of the procedures performed, whereas a transbronchial brush was only diagnostic in 37.8% of the procedures performed. (7) It is important to note that a comparison between different studies is not always admissible. The diagnostic yield of a certain procedure can range dramatically between different studies due to factors such as patient population, size and location of lesions, and operator experience. It is also important to note that the probability of malignancy for small peripheral nodules is significantly lower compared to larger lesions (9). In fact, for lesions <10mm, the malignancy rate is 32.5%, while for lesions >20 mm the malignancy rate is 85%. Hence, diagnosis of small nodules will most likely require a long follow-up period in order to obtain a definite diagnosis.
The combined diagnostic accuracy of a medical technique, such as diagnostic bronchoscopy, should be measured at the end of a follow-up period according to its sensitivity and specificity. The sensitivity test measures the ability of a technique to correctly identify those patients with the disease (true positive rate), whereas the specificity test measures the ability of the technique to correctly identify those patients without the disease (true negative rate). The Sensitivity will be calculated based on the following values:
True Positive (TP) refers to the samples that were positive after the procedure and continued to be positive at the end of the follow-up period
True Negative (TN) refers to samples that were negative following the procedure and had a negative result at the end of the follow-up period
False Negative (FN) refers to samples that were negative after the procedure but turned out to be positive at the end of the follow-up
True Negative (TN) refers to samples that were positive after the procedure but turned out to be negative at the end of the follow-up period
Sensitivity is calculated by: TP/SUM(TP+FN)
Specificity is calculated by: TN/SUM(TN+FP)
Knowing the diagnostic yield of interventional diagnostic medical techniques is important for technique optimization with respect to modalities and tools or combinations of techniques to be used in order to obtain a quality biopsy sample that will provide a definitive diagnosis. The number of available lung diagnostic techniques, imaging modalities, and tools is growing, and a variety of approaches are offered; however, the decision to use a specific combination of techniques, modalities, and tools should be based on their diagnostic accuracy, effectiveness, and operation in order to obtain a high diagnostic yield.