Survey 2004RD: Rapid Diagnostic Techniques for Malaria

Survey 2004RD: Rapid Diagnostic Techniques for Malaria Date 9/11/20 

The November 2020, RDT survey directs partcipants to read the Malaria rapid diagnostic test performance. Results of WHO product testing of malaria RDTs: round 8 (2016-2018). This can be found at https://www.who.int/malaria/publications/atoz/9789241514965/en/ 

The document gives an overview of findings from rounds 5-8 of Malaria RDT product testing. This is a good guide for laboratories on choosing an RDT kit that is likely to perform to a high a standard The document gives in detail how these RDT kits were evaluated. A simple summary is given in this flowchart.

Kits were assessed based on the following: -sensitivity, to detect nearly all clinically significant cases of malaria; - specificity, to accurately discriminate non-malarial febrile illness from malaria in order to ensure appropriate management and accurate disease monitoring; - stability, to maintain accuracy after transport and storage in ambient conditions; and - ease of use and adequate labelling and instructions for use to ensure safe, correct preparation and accurate interpretation of results.

The results are too extensive to document here, but I will be looking at my own laboratory kit and comparing it’s performance to others on the market, based on these findings.

A Rare One!

Quite a rare one here... I had to look it up! Pearson’s Syndrome.. it’s a Congenital Sideroblastic anaemia and Pancreatic dysfunction. I was trying to work out why this patient had macrocytic red cells and thrombocytopenia. Reading around this, it seems that these features are consistent with this form of sideroblastic anaemia. I usually associate sideroblastic anaemia with microcytes and dimorphic red cells and hadn’t appreciated that mainly macrocytes could be a feature and how many different types of sideroblastic anaemia there actually were. Reading about this, it seems that a good starting point in searching for the cause of sideroblastic anaemia is to look at the MCV. So MCV is important! Bottomley, S. Leung L. Tirnauer, JS. (2020) Causes and the Pathophysiology of the Sideroblastic Anaemias

I also saw these. Pappenheimer bodies, which are blue iron containing inclusions in the red cell, and often found near the edge , I usually scan for these when I have a patient with an unexplained anaemia and dimorphic red cells. A lot learnt today! I’ll be using this blood film in morphology training to demonstrate the diversity of red cell size in the Sideroblastic Anaemias.

Malaria Parasitaemias

Dr Samuel Boadi who led Monday’s UK NEQAS Blood Parasitology course, made a very good suggestion for speeding up the calculation of Malaria percentage parasitaemias, in a busy laboratory. The laboratory should establish it’s own average number of red cells per field when using a x100 objective. This average number can be used every time, rather than the microscopist calculating it separately on every occasion. I’m going to ask number of different colleagues to count how many red cells they see on a film using a x100 objective, and take an average. I’ll fill out a quality improvement notice and see if this could be used and added to our SOP, as it will significantly improve turn around times!  

WORMS!!!!

I took a photo of this Microfilaria on last months Parasitology NEQAS. It was indeed Loa Loa. I find this species the easier one to diagnose, mainly because the sheath gives just a halo impression when stained with Giemsa (requires haematoxylin to be seen) and that the nuclei extend right to the tip of the tail. This coincided nicely with today’s UK NEQAS yearly parasitology course, which I attended online. Dr Samuel Boadi, gave a simple breakdown of the features of the tail, in three Filariasis species.

I’ll remember this now, Wucheria Bancrofti- nuclei do not extend to the tip of the tail, whereas Loa Loa, they do. Brugia Malayi is quite distinct with two nuclei separated from one another. Interesting on the NEQAS expert comment, it was suggested that Filaria can be seen macroscopically on a slide. My colleague described it as almost looking like an eyelash. I’m going to have another look, see if I can spot them!

Digital Morphology 2004DM 04/10/20

Digital Morphology 2004DM CPD date 04/10/20 

 I got this right! Myeloproliferative disorder transformed to Acute Megakaryoblastic Leukaemia. 

 I love the training links on the UK NEQAS digital morphology website. Take a look https://www.instagram.com/haematography/, really useful for anyone involved in blood cell morphology.

 I particularly found useful, the guidance on when to use the term 'Megakaryocyte fragment' and when to use the term 'Giant platelet'. Megakaryocyte fragments are basophilic, often atypical in shape, may be vacuolated and lack granules. A giant platelet however is enlarged but has very typical platelet features.

Another learning point from the case narrative was that the heavy granulation (what I would call toxic granulation) in this case, may not neccessarily be due to infection or inflammation, but yet another bizarre abnormaility. A point that I had not previously considered. 

 The narrative also mentions that the fragments seen are not associated with with an acute microangiopathic haemolytic anaemia (MAHA), as they are note sharp in appearance. The bizarre shaped fragments seen here are found in Dyserythropoiesis. I have personally however, seen blunt red cell fragments in TTP but I accept the bizarre shapes are not a feature of MAHA.

Lots of learning points on this film.

COVID-19 and Haemostasis

https://www.werfen.com/uk/en/covid-19-and-implications-haemostasis-and-viscoelastic-testing Read this article today produced by Werfen, which highlighted the effects of COVID-19 on haemostasis. Haemostasis testing has become important in the management of these patients, particularly the severe cases. It discusses how D-Dimer, Prothrombin Time, platelet count and Fibrinogen are of particular use in hospital admissions. COVID-19 causes the following changes in Haemostais tests.

It also discusses how D-Dimer, prothrombin time, platelet count and Fibrinogen are of particular use in determining hospital admissions.

It seems that all COVID-19 patients are treated with low molecular weight infractionated heparin to reduce the risk of thrombotic complications.

Oxidative stress and Haemolysis

So here we go, my first Post! 

 I recently looked urgently at this blood film on a neonate with unexplained anaemia. The striking feature of this blood film for me, were large numbers of irregularly contracted cells. Irregularly contracted cells in large numbers can be seen in a red cell enzymopathies or Haemoglobin C. In the case of red cell enzymopathies they are likely to be accompanied by keratocytes (bite cells) and hemighosts. In the case of Haemoglobin C, target cells would also be a prominent feature. 

 I think this is a classic a oxidative hemolysis picture, because of the large numbers of irregularly contracted cells, polychromasia and keratocytes. We are awaiting results of the G6PD assay as a possible cause. Reading up on the process involved here, it seems that G6PD has a protective role on the red blood cell, and prevent reactive oxygen species, the byproduct of normal cell fuctions, from building up to toxic levels. If this enzyme is lacking, infections, drugs and fava beans can increase levels of reactive oxygen species, causing red cells to be destroyed faster than the body can replace them. Interestingly however this patient was female, and G6PD deficiency occurs predominantly in hemizygous males, although deficiency can occur in homozygous females. 

 We will wait and see the outcome of the results!