# [E1: Investigation Of Errors]{.underline}

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  **Pattern of  **Possible causes**  **Suggested Investigation Steps**
  errors**                           

  HFP and HFN   1\. Unusable         1\. Examine a 3+ using that microscope
                microscope           

                2\. Staining         2\. Check stains and staining
                problems             procedure

                3\. Technician       3\. Test with clear-cut pos. / neg.
                cannot recognize AFB and good microscope

                4\. Gross neglect    4\. Exclude other causes

  A single HFP  1\. Administrative   1\. Compare lab-register with
                error                QC-listing: correct slide number &
                                     result?

                2\. As for more      2\. Exclude causes of more frequent
                frequent HFP         HFP

  Regularly a   1\. Poor             1\. Check accuracy of lab-register and
  HFP with or   registration routine other record keeping

  without LFP   2\. Staining         2.Check stains and staining procedure,
                problems/Fading      consider restaining for rechecking

                3\. Technician       3\. Look for inconsistent results of
                unclear on AFB       suspects (regularly single pos. / low
                appearance           positive) in lab register

  Rare LFP      To be expected       No investigation unless numbers
                                     increase

  Many LFP,     1\. Problem with     1\. Evaluate controllers
  with          controllers          

  or without    2\. Technician       2\. Recheck special sample of LFP from
  occasional    unclear on AFB       laboratory register
  HFP           appearance           

                3\. Contaminated     3\. Test stain with known negative
                stain reagents       smears

  Single HFN    1\. Administrative   1\. Compare lab-register with
                error                QC-listing: correct slide number &
                                     result?

                2\. Very thick       2\. Evaluate quality of smear
                smears and/or poor   preparation, check microscope
                light                

                3\. Gross neglect    3\. Exclude other causes

  Frequent HFN  1\. Staining         1.Check stains and staining procedure,
  and/or        problems/Fading      consider restaining for rechecking

  Many LFN      2\. Poor             2\. As above, single HFN
                smearing-technique   

                3\. Problems with    3.Check microscope with positive slide
                microscope           

                4\. Careless         4\. Exclude other causes
                microscopy           

                5\. Contaminated     5\. Test stain with known negative
                stain reagents/water smears

  Very high     Contaminated meth.   As above
  proportion    blue or rinse water  
  LFN                                

  Many QE       1\. Poor staining    As above

  (too low      2\. Problems with    As above
  gradings)     microscope           
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