Study setting
This study was conducted in Tigray region, Northern part of Ethiopia. Tigray has an estimated total population of 4.8 million people over an area of 50,078.64 square kilometers. Based on the 2007 census projection, majority (80.5%) of the population live in rural areas, while 19.5% are urban dwellers [13]. There were about 57 medium and above private health sectors provided AFB smear microscopy in Tigray region. Of these, 27 health facilities were enrolled and participated in EQA of random blinded rechecking program for AFB smear microscopy. This study was conducted in private health facilities that were enrolled in random blinded rechecking program. But, unfortunately the study was conducted in 10 private health facilities which have proper stored smear slides for blinded rechecking during the study period. The study sites included 2 General hospitals, 4 health centers, 3 specialty clinics and one medium clinic found all over the region.
Study design and period
Facility based cross sectional study was conducted from April 1st, 2017 to May 30, 2017 in selected private health facilities in Tigray region, Northern Ethiopia.
Study Population
Private health facilities which were enrolled and participated in external quality assessment of random blinded rechecking program for AFB smear microscopy.
Sample size and sampling technique
This study included private health facilities which were enrolled in EQA of random blinded rechecking for AFB smear microscopy. The smear slides for blinded rechecking were collected using LQAS method which is a valid statistical sampling with the assumption a sensitivity of 80% , specificity of 100%, zero acceptance number and 95% confidence interval from routinely collected and stored slides [14].
Data collection Techniques
The data was collected using standard blinded rechecking data collection tools. The blinded rechecking smears were collected based on the LQAS method from routine stored smear slides in microscopic center [14]. Once the smear slides were collected at peripheral, and then transported and reread by senior laboratory technology in Tigray health research institute. If discrepant results occurred a second controller was assigned and the final result was generated from this. Finally, all the discordant results were communicated to health facilities.
Definition of terms
Low False Negative (LFN); Scanty or actual number (1 to 9 AFB /100 fields) positive smear misread as negative.
Low False Positive (LFP); A negative smear misread as a scanty (1 to 9 AFB / 100 fields) positive.
Quantification error (QE); Is a positive smear reading when the difference in smear grading report is greater than one between the examinee and controller
High False Negative (HFN); Smear positive with 1+ to 3+ grading or bacilli density misread as negative.
High False Positive (HFP); a negative smear misread as smear positive with bacilli density 1+ to 3+.
Major error: Indicated by HFP and or HFN errors; this type of error is considered the most critical since it has the highest potential impact on patient management, and can result in an incorrect diagnosis or improper management of a patient.
Minor error: Type of errors included LFP, LFN and QE, in clinical practice; these errors may have some impact on patient management. But, for the purpose of evaluating laboratory performance, this type of error is considered less serious, because of the inherent limitations AFB smear microscopy in detecting or few unequally distributed AFB within a smear.
Controller; Supervisory laboratory or technician responsible for rechecking slides.
Statistical analysis
All data was entered into an excel spreadsheet, and then transferred for statistical analysis using SPSS version 25. By considering the reference smear reading results as a gold standard, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of AFB smear reading was determined using 2 x 2 contingency table. The smear reading agreement was also calculated using kappa statistics test.
Ethical approval
Ethical clearance was obtained from Tigray Health Research Institute, Institutional Review Board (THRI, IRB). Official letter was obtained from Tigray health research institute. Permission was also obtained from the study area.