October 7 2010 (Thursday) - Hereditary Spherocytosis

A patient reported for ante-natal clinic at which a blood count was performed. She proved to be a tad anaemic, and the analyser suspected nucleated red cells (which isn’t an uncommon thing for it to suspect in pregnancy). For these reasons a blood film was made, and spherocytes were seen.

DOB  29/09/1977 Sex F Pat No 666999        Source    ANC      Received  12:58
Address   SOMEWHERE IN EUROPE,            Clinician WHO            07/10/2010
Specimen No : AW203214B    (Haematology)           

07/10/2010 11:15  EDTA
  Haemoglobin               10.7           g/dl         (  11.0 to 15.0  ) Auth
  White Blood Cells         10.5           10^9/l       (     4 to 11    ) Auth
  Platelets                 414            10^9/l       (   150 to 400   ) Auth
  Red Blood Cells           3.55           10^12/l      (   3.8 to 4.8   ) Auth
  Haematocrit               0.320          ratio        (  0.36 to 0.46  ) Auth
  Mean Cell Volume          91.3           fl           (    80 to 100   ) Auth
  Mean Cell Haemoglobin     30.1           pg           (    27 to 32    ) Auth
  Mean Cell Haemoglobin Con 33.0           g/dl         (    32 to 36    ) Auth
  Neutrophils               7.7            10^9/l       (     2 to 7.5   ) Auth
  Lymphocytes               2.0            10^9/l       (   1.5 to 4     ) Auth
  Monocytes                 0.6            10^9/l       (   0.2 to 1     ) Auth
  Eosinophils               0.2            10^9/l       (  0.02 to 0.5   ) Auth
  Basophils                 0.0            10^9/l       (     0 to 0.1   ) Auth
  XE FLAG1                  Spherocytosis ++                               Auth
  XE FLAG2                  ^A blood film has been reviewed                Auth

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The patient’s (real) name rang a bell – I knew this patient had hereditary spherocytosis. This is a condition in which the patient’s red cell survival is decreased because of a problem with red cell membrane structure. Rather than being biconcave discs, the patient’s cells are spherical. Therefore not so flexible, and don’t live as long. Normally this condition is well compensated, but when the patient is unwell for other reasons, the HS can be aggravated and cause an anaemia.

Usually spherocytes are detected microscopically. In the case above a blood film was made because blood count parameters fell outside the reference range, and the automated analyser suspected nucleated red cells (which isn’t uncommon in pregnancy).
However I’m left wondering. Someone with HS having a blood count for any other reason may well have normal numerical results (it happens!), and with no blood film being made, the condition would go unnoticed. In fact the patient under consideration has had six previous blood counts over the last three years, none of which triggered the making of a blood film by the automation.

So we have a potential failing in the system. We are (potentially) not finding cases of hereditary spherocytosis. At first thought I was rather concerned, but then again, does this actually matter? Many cases of HS (and the related HE) are often not clinically significant. Some patients with these conditions can (and do) go their entire lives with absolutely no problems being generated by the well-compensated haemolytic process.

It was suggested that cases of HS have raised reticulocytes and so we could use that as a pointer, but performing reticulocyte counts on every blood count would get rather expensive and would slow the process down. In conversation with colleagues it was suggested that the spherocytic cells may well scatter light differently to biconcave discs, and that maybe one of the XE channels might find spherocytes. I relayed this suggestion to the analyser’s manufacturer who said not, but they were rather flummoxed by this problem. After some discussion we came to the conclusion that a case of HS which actually needs to be diagnosed will present either clinically with jaundice and/or anaemia, or will have an obvious problem with the blood count. And in 99.9% of the time will be suspected from a family history.
So there’s no need to change practice (at the moment…)

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