The following blood results were obtained from a previously fit and well patient undergoing a prolonged respiratory wean following an episode of severe community acquired pneumonia one month earlier.
|
Parameter |
Patient Value |
Adult Normal Range |
|
Haemoglobin |
78 g/L* |
115 – 155 |
|
Haematocrit |
0.20* |
0.35 – 0.45 |
|
Mean Cell Volume |
85 fL |
80 – 99 |
|
Mean Cell Haemoglobin |
28 pg |
27 – 33 |
|
White Cell Count |
15.3 x 109/L* |
4.0 – 11.0 |
|
Neutrophils |
12.0 x 109/L* |
1.9 – 7.5 |
|
Platelets |
758 x 109/L* |
150 – 400 |
|
Reticulocyte count |
40 x 106/L |
30 – 130 |
|
Iron |
8 mmol/L* |
10 – 30 |
|
Ferritin |
798 mg/L* |
20 – 450 |
|
Transferrin saturation |
0.10* |
0.15 – 0.50 |
|
Vitamin B12 |
700 pmol/L |
200 – 900 |
|
Folate |
15 nmol/L |
> 7 |
|
C-reactive protein |
210 mg/L* |
< 8 |
|
Albumin |
25 g/L* |
35 – 50 |
a) Interpret the abnormal results and justify your reasoning. (4 marks)
Syllabus topic/section:
2.1.6 Gastrointestinal Intensive Care / Acute hepatic failure: L1
2.1.5 Renal Intensive Care / Acid base and electrolyte disorders: L1
2.1.11 Haematological and Obstetric Intensive Care / Anaemia: L1
2.1.12 Obstetric Intensive Care: / Physiological change related to pregnancy: L1
Discussion:
This was a repeat data interpretation question. Surprisingly the pass rate was low for this question. Lower scores were associated with not being specific about causes of hyperammonemia, but rather listed causes of hepatic dysfunction. A lack of synthesis of findings was also a feature of the answers failing to reach the standard required.
This was indeed a repeat of Question 9.2 from the first paper of 2017. It is such a repeat that even the ancient "interpret" and "justify" terminology remains unchanged, an anachronism in this era of vocabulary terms (it would have been "list" and "explain" in the modern era).
In 2017, the college left us with a model answer, which looked like this:
Normochromic normocytic anaemia of chronic disease with on-going inflammation NOT Fe deficiency anaemia because:
• Normochromic normocytic anaemia
• Low Fe
• Transferrin saturation mildly reduced.
• Raised ferritin.
• Raised CRP (inflammatory state)
The abnormalities are as follows:
This is consistent with an anaemia of chronic disease, which is usually a microcytic hypochromic affair (i.e MCV and MCH is usually lower in those cases). The reticulocyte count is typically low, which indicates underproduction of red cells. This comes from the review article by Weiss and Goodnough (NEJM, 2005)
For each of these "interpret iron studies" questions, this table ends up in the discussion section:
| Condition | MCV | MCHC | Serum iron | Ferritin | Transferrin | Transferrin saturation |
TIBC |
| Iron deficiency anaemia | low | low | low | low | high | <20% | high |
| Anaemia of chronic disease | low | low | low | normal | low | normal | low or normal |
| Acute phase response | normal | normal | low | high | low | low | low |
| Iron overload | normal | normal | high | high | normal | high | high |
Hawkins, Stephen F., and Quentin A. Hill. "Diagnostic Approach to Anaemia in Critical Care." Haematology in Critical Care: A Practical Handbook (2014): 1-8.
IRON STUDIES STANDARDISED REPORTING PROTOCOL - RCPA, 2013
Hearnshaw, Sarah, Nick Paul Thompson, and Andrew McGill. "The epidemiology of hyperferritinaemia." World journal of gastroenterology 12.36 (2006): 5866. - ! WARNING ! this link will download the whole September issue, with the potential to fatally clog your internet hole.
Weiss, Guenter, and Lawrence T. Goodnough. "Anemia of chronic disease." New England Journal of Medicine 352.10 (2005): 1011-1023.
Koepke, J. F., & Koepke, J. A. (1986). Reticulocytes. Clinical & Laboratory Haematology, 8(3), 169–179.