Although they frequently present together, iron deficiency and anaemia can occur independently of one another. The absence of anaemia, therefore, cannot rule out iron deficiency, and vice versa. Care must be taken to distinguish between three similar, but separate conditions: iron deficiency without anaemia, iron deficiency with anaemia, and anaemia without iron deficiency (see also ‘Screening’).
There are two types of iron deficiency that represent different kinds of iron impairment. The two variants can be distinguished by their differing serum ferritin measures1.
Symptoms can vary depending on the type of iron deficiency, the presence of concomitant diseases, and the severity of the deficiency. In some cases, few clinical symptoms may be present until a severe disease status is reached.
The commonality between symptoms of iron deficiency, with or without anaemia, and those of concomitant diseases may also complicate diagnosis and reliance upon symptoms alone is not appropriate. Comprehensive screening of multiple blood iron parameters is the only method of accurately diagnosing iron deficiency.
Each therapeutic area has its own guidelines detailing the common presentation of iron deficiency within specific patient populations. More information can be found in the ‘Clinical guidelines’ section of Iron Essentials. For recent news relating to the identification of iron deficiency within the various different therapeutic areas please go to the 'Identification and diagnosis' tag.
The most common method of screening for iron deficiency is to look for changes in haemoglobin level. However, this measurement alone is not sufficient to diagnose iron deficiency, as an individual may be low in iron yet have a haemoglobin level in the normal range (see figure below). In addition, haemoglobin levels are highly variable and have been shown to fluctuate with age and gender, at different stages of pregnancy, and with altitude and smoking. There is also evidence that haemoglobin concentration is influenced by genetic variation.
Copyright permission obtained from Beard et al, 2001.
The correct identification of iron status requires information from multiple blood tests, including analysis of haemoglobin, ferritin and transferrin saturation, and clinical assessment. As each test represents a different aspect of iron metabolism, care must be taken when interpreting the results and selecting threshold values. Approximate values for a number of common diagnostic tests are shown in the table below6; however, the appropriate guidelines should always be adhered to when determining specific diagnostic cut offs.
Table 4. Commonly used thresholds for blood iron parameters6