Table 3

Discrepant TB-bead FM results compared with culture: results of direct ZN and concentrated FM, and blinded re-checking of Magnetic bead results

Lab No

Direct ZN

Conc FM

Magnetic bead-FM

Magnetic bead re-read*


Magnetic bead false positives (compared to culture)


261

Negative

Negative

3+

3+


206

Negative

Negative

1 AFB/40F

Negative


099

Negative

Negative

1 AFB/40F

Negative


259

Negative

Negative

3+

3+


296

Negative

Negative

8 AFB/40F

Negative


082

Negative

1+

13 AFB/40F

Negative


276

Negative

Negative

2 AFB/40F

Negative


203

Negative

Negative

1 AFB/40F

Negative


287

Negative

Negative

1 AFB/40F

Negative


262

Negative

Negative

1 AFB/40F

3+


141

Negative

Negative

1 AFB/40F

2 AFB/40F


256

Negative

Negative

2 AFB/40F

13 AFB/40F


096

Negative

Negative

1 AFB/40F

8 AFB/40F


180

Negative

Negative

3 AFB/40F

1 AFB/40F


131

Negative

Negative

1 AFB/40F

1 AFB/40F


299

Negative

Negative

3+

1+


302

Negative

Negative

2 AFB/40F

3+


211

Negative

1+

4 AFB/40F

Negative


267

Negative

Negative

2 AFB/40F

3 AFB/40F


299

Negative

Negative

2 AFB/40F

1+


Magnetic bead false negatives compared to culture (with one or more positive result by conc FM or ZN)**


283

5 AFB/40F

2+

Negative

1+


280

2 AFB/40F

2+

Negative

2 AFB/40F


260

1+

2+

Negative

1+


258

6 AFB/40F

3+

Negative

Negative


151

1+

3+

Negative

Negative


084

1+

1+

Negative

Negative


294

Negative

15 AFB/40F

Negative

Negative


292

Negative

5 AFB/40F

Negative

3 AFB/40F


210

Negative

2 AFB/40F

Negative

Negative


157

Negative

8 AFB/40F

Negative

Negative


034

Negative

5 AFB/40F

Negative

Negative


053

Negative

1+

Negative

Negative


050

Negative

3+

Negative

3 AFB/40F


011

3 AFB/40F

Negative

Negative

4 AFB/40F


* Slides were blindly re-checked

**An additional 23 specimens had false negative results by all three microscopy methods and re-checking was not performed.

Albert et al. BMC Infectious Diseases 2011 11:125   doi:10.1186/1471-2334-11-125

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