Authors (including presenting author) :
Cho WF(1), Ling KH(1), Chau KY(2)
Affiliation :
(1) Clinical Laboratory Department, Haven of Hope Hospital; (2) Department of Pathology, United Christian Hospital
Introduction :
Tuberculosis is a common disease in Hong Kong. Rapid diagnosis is critical for initiation of treatment and infection control measures. Mycobacteria are acid-fast bacilli (AFB) which can be detected by microscopic examination of fluorescence or Ziehl-Neelsen stained smears. Manual microscopic screening can be tedious, time-consuming, and results can be affected by human factors like user proficiency, number of searched Field-Of-Views, and weariness of staff. Documentation is restricted to the storage of the sample itself. MetaSystems is an automated slide scanning platform for screening of AFB smears, which can improve workflows, reduce labor cost and minimize discrepancy due to human factors. It can automatically load slides onto a microscope, focus and digitally capture images to identify AFB. The actions are defined by sets of parameters bundled up in customizable classifiers. Archived digitized data are easy to be tracked and recalled.
Objectives :
Comparison of AFB smear results obtained by Manual Microscopy and Automated Microscopy System
Methodology :
1.Determination of the performance of the automated microscopy system. A total of 896 samples had been included in the study. Smears prepared from samples were screened for AFB by both MetaSystems and manual microscopic examination. The sensitivity and specificity of the MetaSystems were calculated with reference to the manual screening. 2.Determination of the detection limit (LOD). Smears were prepared with serial dilution of a suspension of Mycobacterium tuberculosis ATCC 25177. The smears were then scanned by the MetaSystems to determine the LOD
Result & Outcome :
1.The data showed that the automated system demonstrated >90% agreement with manual microscopy in the correlation study. The sensitivity is 100% (22/22) and the specificity is 95.7% (836/874). When compare to culture results, seven culture positive cases were picked out by MetaSystems, which were screened negative by manual microscopy. This might indicate a potential higher sensitivity of the automated system 2.The LOD is 5000 CFU/ml, which is comparable to manual microscopic examination. Our Laboratory is the first clinical laboratory among public hospitals in Hong Kong to implement the MetaSystems in the routine workflow for AFB smear screening. The automated microscopy system is non-inferior to manual screening and is considered to have satisfactory performance with potentially higher sensitivity. More than 200 unattended smear screening can be performed during non-working hours. Discrepancies due to human factors can be minimized. 70% of technical time for manual microscopy can be saved as only smears detected positive require further confirmation with manual method. In conclusion, this system can improve service quality and enable earlier detection of patients with tuberculosis for appropriate management.
