In health no more than 1-2 % of total hemoglobin is present as methemoglobin. This is a dysfunctional form of hemoglobin that is unable to bind and transport oxygen because the iron atom of the heme moiety is in the ferrous rather then the normal ferric state. Abnormal increase in methemoglobin, a condition called...

Increased serum bilirubin (hyperbilirubinemia) and consequent jaundice are common during the neonatal period. Around 50 % of newborns develop some degree of jaundice, during the first week of life, but for the vast majority this is mild (serum bilirubin peaking no higher than 150-200 µmol/L) and spontaneously resolves ...

Arterial blood is the standard sample for blood gas analysis but arterial blood sampling is more painful and hazardous to the patient. Such is the relative convenience and safety of sampling venous blood that several studies have sought to investigate the validity of its use as a substitute for arterial blood.  The...

Results of hemoglobin (Hb) and hematocrit (Hct) measurement are routinely used to assess blood loss among trauma patients. But is it necessary to measure both parameters and if not, is one more reliable than the other? There is evidence to suggest that many physicians believe hematocrit is a more sensitive indicator...

Despite the fact that self-monitoring of blood glucose (SMBG) apparently accounts for an amazing 20 % of the expenses of the total in vitro diagnostic market worldwide (27 % in the US), there remains a woeful lack of evidence that SMBG is actually effective in improving the clinical outcome of diabetic patients.  In...

Plasma sodium and chloride concentration are routinely measured using either a direct or indirect ion-specific electrode (ISE). Direct ISE is the technique employed in blood gas and most other point-of-care analyzers whereas indirect ISE is used in the majority of biochemistry profiling analyzers sited in central...

The critical significance of the preanalytical phase of blood testing is highlighted by the tragically fatal case of an intensive-care patient who was given an inappropriately high dose of insulin following a falsely high blood glucose result. The patient was recovering from multiple organ failure following surgery in ...

Clinical laboratories should have a policy mandating staff involved in analysis of patient samples to convey critical results to clinical staff urgently, usually by telephone. A critical result has been defined as a result "at such variance with normal as to be life threatening, unless something is done promptly, and...

Accurate blood gas results depend on a homogeneous blood sample and the necessity for thorough mixing of samples is reflected in written standard operating procedures for blood gas analysis. The results of a recent study suggest, however, that manual mixing techniques routinely used may be inadequate in achieving a...

Acid-base physiology and significance of blood gas results are topics that many students find daunting. Their difficulty is not aided by the non-standard abbreviations used to indicate partial pressure of a gas. The issue is highlighted in a recent letter to the journal Clinical Chemistry.  The authors cite the...