(2) Slides keeping or sending
PMC must keep all the positive slides and part of negative slides until TB coordinator or supervisor visits to collect them for QC or asks to sent them. However, it is desirable to keep no more than 200 negative slides from the last day of examination. The slides must be clearly and systematically labeled and kept positive and negative slides separately but in order consistent with the laboratory registry book (or logbook). If PMC send the slides, they have to send a list which must be filled with the slide labellings and microscopy results in a consistent order of laboratory registry book.
(3) Selection of smear slides
The number of slides for rechecking should be minimum enough to measure an acceptable sensitivity and specificity. If 1/3 of smear slides for rechecking are positive (P=33%), and if we check the proficiency of smear microscopy taking account of 5% of a-error, 10% of B-error, and 25% of tolerance level (E), the number of slides requiring for recheck is 30 [N=(Za+Zn)2.P.(I-P)/E2]. Thus, 30 smear slides (10 positive/20 negative slides) may be enough at one time evaluation. From the operational point of view, more than 30 slides may impose too much work to higher level laboratory. TB coordinator or supervisor should cross-check the labels of smear slides with the laboratory logbook beforehand in order to confirm whether they kept all the slides and in a consistent order.
It is recommendable to select one positive slide of every cases for QC but no more than 10 slides at one time evaluation and 20 negative slides randomly from the slide boxes. If the positive slides are selected less than 10 slides, then negative slides can be selected more until the total number of slides become 30. The 30 selected slides should be placed in a box by appropriately mixing the positive and negative slides. And the smear check Forms 1 (see below) is filled up entering the laboratory serial numbers and reading results of the selected slides in the order of their serial placement in a slide box and then serial QC numbers are given by TB coordinator.
