November 29 2010 (Monday) - The R.D.W. Revisited


On November 1 I reflected on the use of the R.D.W. as a useful laboratory result.It’s since been pointed out to me that many labs report R.D.W. in place of M.C.H.C. since the R.D.W. is of far more diagnostic importance, and on pre-printed lab reports there is only so much space. Adding an R.D.W> result would mean that something else would have to go.

I thought about that for a bit, but today found something of interest. Consider this set of results:

                             Specimen Results Entry

Mouse, Mickey                                               
DOB  01/01/1930 Sex F Pat No 123456       Source    CJ2     
Address   EuroDisney                  Clinician HOSJ     
Diagnosis ?pe.....
Specimen No   :  AW198831V               Selected Auth Level : S
--------------------T-------------------T-------------------T-
 HB     10.4   F000 |MONO   0.9    F000 |~F8   ^            |
 WBC    8.4    F000 |EOS    0.0    F000 |~F9   ^            |
 PLT    408    F000 |BASO   0.0    F000 |~F10  ^            |
 RBC    2.70   F000 |~F1   ^TURB   F008 |                   |
 HCT    0.260  F000 |~F2   ^FILMW  F008 |                   |
 MCV    95.9   F000 |~F3   ^            |                   |
 MCH    38.5   F000 |~F4   ^            |                   |
 MCHC   40.2   F000 |~F5   ^            |                   |
 NEUH   4.9    F000 |~F6   ^            |                   |
 LYMPH  2.5    F000 |~F7   ^            |                   |
--------------------T-------------------T-------------------T-
LTG comments : F,FR
 

From the M.C.H.C. this is clearly a case of cold agglutinins. For information the RDW – SD  was 44.9 fl and the RDW – CV was 15.6 %. On warming the sample, the following (far more plausible) results were obtained:


                             Specimen Results Entry

Mouse, Mickey                                               
DOB  01/01/1930 Sex F Pat No 123456       Source    CJ2     
Address   EuroDisney                  Clinician HOSJ     
Diagnosis ?pe.....
Specimen No   :  AW198831V               Selected Auth Level : S
--------------------T-------------------T-------------------T
 HB     10.3   S000 |MONO   1.0    S000 |                   |
 WBC    9.7    S000 |EOS    0.1    S000 |                   |
 PLT    399    S000 |BASO   0.0    S000 |                   |
 RBC    3.42   S000 |~F2   ^FR     S008 |                   |
 HCT    0.310  S000 |                   |                   |
 MCV    89.5   S000 |                   |                   |
 MCH    30.1   S000 |                   |                   |
 MCHC   33.7   S000 |                   |                   |
 NEUH   5.6    S000 |                   |                   |
 LYMPH  2.9    S000 |                   |                   |
--------------------T-------------------T-------------------T
LTG comments : F,FR




RDW – SD was 45.5 fl and RDW – CV was 14.4 %. The M.C.H.C. is significantly improved, but the R.D.W. parameters are effectively unchanged. Bear in mind that the Sysmex XE Aniso flag doesn’t kick in until RDW – SD >65fl and/or  RDW - CV >20.

So were we to replace M.C.H.C. with R.D.W. then I think we would have the potential to miss cases of cold agglutinins. Current practice is (again) vindicated….

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