CNN model trained by large datasets has been proved to be able to achieve human-level ability in identification and classification of various medical images, such as detecting the classification of diabetic retinopathy[8, 27, 30]. However, there is not an AI-based device that is currently in use of BM morphology assessment in clinical laboratories.
The morphology of BM nucleated cells varied in different pathological conditions, thus the Morphogo system’s analytical performance was evaluated in 19 types of hematological diseases. Due to small numbers of cases in certain pathological conditions, the BM smears were divided into five groups (G1-G5) according to degrees of cell morphology changes. In this study, the G1 was made up of leukemia with a significantly increased of blasts in the BM including MDS-AL, AML, ALL, CML-AP and malignant lymphoma [31–33]. The G2 consisted of MA, PCM, MDS, CML and MPN. Cells in these diseases has moderate or obvious morphological changes. MA is characterized by the presence of megaloblast in BM due to mature asynchronously between nucleus and cytoplasm [34]. Plasma cells in PCM are highly pleomorphic, such as diffuse sheet growth pattern and immature cell morphology[2]. MDS or MPN is usually characterized by dysplasia in one or more myeloid lineages in BM [35, 36]. CML is a kind of cancer with an uncontrolled increased in the number of myeloid cells [37]. Hematological diseases in G3 were accompanied by mild changes in BM nucleated cell morphology, including ITP and CLL. ITP is an acquired autoimmune disease with increased platelet destruction and decrease platelet production [38]. B lymphocytes debris is a morphology feature of CLL [39]. IDA, SA, SL, and AA were classified into G4, and these diseases are basically not accompanied by cell morphological changes [40–42]. The G5 was dilution cases. The diagnostic results that pathologists made based on Morphogo system’s morphological findings were compared with the original cytology diagnoses based on manual microscopic examination. Morphogo system displayed a good ability to assist diagnosis in all groups (G1-G5), which were higher than those of prior studies reported [1, 13, 23, 25, 43]. Furthermore, the diagnoses made by pathologists using Morphogo system were consistent with the diagnoses of microscopic examination, as evidenced by the Kappa value of more than 0.85. It showed that Morphogo system is a useful tool for diagnosis of hematological diseases.
The study provided doctors with a potential way to apply AI to the morphology examination of BM smears. However, as the previous research reported, even for experienced pathologists, subtle differences between cells with similar morphological characteristics are difficult to identify [27]. This may explain why the sensitivity and PPV performance were not good in the identification of prolymphocyte, but the PPV of prolymphocyte and its similar cells was up to 1.0000. Furthermore, the image quality of BM nucleated cells depends on several factors, including the quality of BM smear preparation, the pathological condition and the imaging process [13]. This may be another cause of inaccurately identification of BM cells. The morphology of blasts in AL of G1 is more uniform, while they are relatively polymorphic and malformed in MDS of G2 [13]. Therefore, the blasts are easier to be identified and classified in AL, and difficult to be identified in MDS, which might be the cause of the higher misdiagnosis rate in some cases of Morphogo system compared with pathologists. Pathologists using Morphogo system made the diagnosis results of 16 cases were inconsistent with that made by conventional microscopes. Since the pathologists also refer to the results of other diagnostic tests when using microscope, such as flow cytometry and BM biopsy to diagnose disease. However, due to the massive number of BM samples every working day and the fact that BM cell differential count is so laborious and time-consuming, in some laboratories, while using Morphogo system they can review AI-based cell differential count results on the computer screen, which will dramatically improve the efficiency of laboratory work. We can imagine that Morphogo system can obtain and analyze more cells in a shorter period of time, and pathologists can review more cells to prevent some critical morphological changes from being missed, thus reducing the misdiagnosis rate and missed diagnosis rate. Meanwhile, it can help hospitals in rural area that lacks pathologists and save time for pathologists.
In this study, we used a single center method, in which all BM smears were prepared in the same laboratory and digitally processed. However, this study still had some limitations. The study was limited to 19 common diseases, and there were not enough number of cases for all of them. For example, there were only 4 cases of CML, 2 cases of CML-AP and lymphoma, so it was uncertain whether Morphogo system’s AI could have the same performance in all kinds of common hemato-pathological diseases and in even more rare conditions. In the future, more studies can be carried out with larger number of BM samples that consist of more types of hematological diseases from multiple laboratories to further validate the BM cell identification performance of Morphogo system.