Microscopist inter-observer agreement. The inter-observer agreement is shown for 2 microscopists for conventional smears and for smears prepared after bleach-sedimentation. Filled circles represent smears prepared from bleach-sedimented sputum (correlation coefficient r = 0.707), and open diamonds represent conventional smears (r = 0.991). The 3 data points encircled by broken lines represent smears prepared from bleach-sedimented sputum found to be clearly positive by one reader but negative by the other reader. Excluding these 3 false-negative results caused the value of the correlation coefficient for results from bleach-sedimented sputum to increase to r = 0.997. The dotted line represents perfect agreement. The boxes parallel with the axes indicate the smear-microscopy grade equivalent to the acid-fast bacilli counts per 100 microscopy fields (0 indicates none visible/100 fields; +/- indicates 1-9/100 fields; + indicates 10-99/100 fields; ++ indicates 100-999/100 fields; and +++ indicates > 1000/100 fields).