Abstract
IntroductionMicroscopy is the gold standard for diagnosis of malaria, however, manual evaluation of blood films is highly dependent on skilled personnel in a time-consuming, error-prone and repetitive process. In this study we propose a method using computer vision detection and visualization of only the diagnostically most relevant sample regions in digitized blood smears.MethodsGiemsa-stained thin blood films with P. falciparum ring-stage trophozoites (n = 27) and uninfected controls (n = 20) were digitally scanned with an oil immersion objective (0.1 µm/pixel) to capture approximately 50,000 erythrocytes per sample. Parasite candidate regions were identified based on color and object size, followed by extraction of image features (local binary patterns, local contrast and Scale-invariant feature transform descriptors) used as input to a support vector machine classifier. The classifier was trained on digital slides from ten patients and validated on six samples.ResultsThe diagnostic accuracy was tested on 31 samples (19 infected and 12 controls). From each digitized area of a blood smear, a panel with the 128 most probable parasite candidate regions was generated. Two expert microscopists were asked to visually inspect the panel on a tablet computer and to judge whether the patient was infected with P. falciparum. The method achieved a diagnostic sensitivity and specificity of 95% and 100% as well as 90% and 100% for the two readers respectively using the diagnostic tool. Parasitemia was separately calculated by the automated system and the correlation coefficient between manual and automated parasitemia counts was 0.97.ConclusionWe developed a decision support system for detecting malaria parasites using a computer vision algorithm combined with visualization of sample areas with the highest probability of malaria infection. The system provides a novel method for blood smear screening with a significantly reduced need for visual examination and has a potential to increase the throughput in malaria diagnostics.
Highlights
Microscopy is the gold standard for diagnosis of malaria, manual evaluation of blood films is highly dependent on skilled personnel in a time-consuming, error-prone and repetitive process
All malaria samples included in the study had previously received a species-specific diagnosis of P. falciparum, as assessed with a conventional microscope by an expert microscopist according to WHO guidelines [6]
The proposed method is evaluated from two perspectives: 1) as a decision support tool that detects parasite-like objects in a digitized thin blood film and presents the most suspicious sample regions to a human observer and 2) as an automated parasitemia estimation tool by classifying segmented erythrocytes as infected or un-infected
Summary
Microscopy is the gold standard for diagnosis of malaria, manual evaluation of blood films is highly dependent on skilled personnel in a time-consuming, error-prone and repetitive process. Accurate malaria diagnosis is a key to successful management of the disease; yet in the African region, in 2012, up to 40% of suspected malaria cases attending public health facilities did not receive a diagnostic test [1]. Fewer than 10% of patients under the age of five presenting with fever are tested [2]. Effective diagnostics improves the management of patients with malaria, supports differential diagnosis regarding fever, and is essential for malaria surveillance reporting. Inappropriate use of costly first-line artemisinin-based combination therapies is reduced resulting in prevention of adverse effects, drug resistance and an improved cost-benefit ratio for the management of febrile symptoms [3]. The drop in the incidence of malaria increases the risk of misdiagnosing febrile illness resulting in a paradoxical increase in the demand for accurate diagnosis [4]. The consequence is failure to adequately treat other causes of fever [5]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call