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….