The packed cell volume (PCV) or haematocrit (Ht or HCT) or erythrocyte volume fraction (EVF) is the proportion of blood volume that is occupied by red blood cells. It is normally about 48% for men and 38% for women. It is considered an integral part of a person's complete blood count results, along with haemoglobin
concentration, white blood cell count, and platelet count. In a normal, healthy bird, the PCV ranges between 35-55%.
Small birds such asbudgies and cockatiels average 50% while the values in larger species are usually lower, around42%. Any value less than 35 indicates anaemia and obviously the lower the value, the morecritical the condition. Values higher than 55% are most often caused by dehydration (Purves et.al., 2004).
The measurement of PCV is so useful in any hematologic workup that its presence in hematologic test panels is taken for granted. It is also a linchpin of quality control programs in the haematology laboratory. Despite this importance, it has received far less scrutiny from the standpoint of its reliability than have the measurements of haemoglobin or red cell counts. The trapping of white cells or plasma will erroneously increase the spun haematocrit, this much is obvious.
The reliability of a particular laboratory method can be discussed meaningfully only if a reference method exists against which the particular working method can be compared.A PCV reference method that can be performed in any laboratory capable of performing a reference haemoglobin determination has now been described.
The existence of this PCV reference method has made it possible to determine the presence and the extent of errors in the spun haematocrit as it is routinely performed in the haematology laboratory. For the sake of clarity, the PCV reference method will be referred to as the PCV; the routine laboratory method will be called the spun microhaematocrit (Brian and Karen 2001).
Determination of the packed cell volume as described by cheesbrough, 2000
EDTA blood sample from each participant was aspirated into micro-haematocrit capillary tubes. One end of the capillary tube was subsequently sealed with plastercin and placed in the micro-haematocrit centrifuge. A steady packing of the red blood cells was achieved with a centrifugation speed of 12000 g for 5 min. The PCV was measured using a Haematocrit reader and reported as a ratio of the whole blood volume in litre/litre (Ezeugwunne et al., 2012).
The detection of PCV is a simple and reliable method for detecting the presence or absence of anaemia or polycythaemia. Indeed the PCV measured by centrifugation is more reliable for monitoring patients with polycythaemia than is the PCV calculated on many automated cell counters (Klee et al, 2000).
ERYTHROCYTE SEDIMENTATION RATE (ESR)
The erythrocyte sedimentation rate (ESR) is the rate of sedimentation of red blood cells (RBCs) and is used often as a nonspecific measure in monitoring disease activity and assisting in the diagnosis of many inflammatory disorders. The ESR is not a well-understood phenomenon and has been described as occurring in 3 phases: RBC aggregation, precipitation, and packing.
RBC aggregation is a critical factor for the sedimentation and is facilitated by the presence of certain plasma proteins called agglomerins, which include fibrinogen, Immunoglobulin M, and α2-macroglobulin. Any factors affecting these 3 phases, including those in the number and shape of RBCs and plasma viscosity, can affect the sedimentation rate. The ESR is expressed as millimeters per hour and varies between age groups and sexes (Bharathi et al., 2011).
Moderately raised sedimentation rate can sometimes be found in healthy people, particularly those living in tropical countries and a normal ESR cannot exclude disease. In many tropical countries, ESR measurements have been discontinued because they add little to diagnosing disease, assessing its progress and monitoring response to treatment. When performed, test results must be interpreted in conjunction with clinical findings and the results other laboratory tests (Cheesbrough, 2006).
Determination of erythrocyte sedimentation rate (ESR) by Westergren as described by Cheesbrough, 2000
0.4ml of sodium citrated anticoagulant was pipetted into a clean test-tube. 1.6ml of the Blood in the EDTA bottle was added into the test-tube and its content mixed. A westergren pipette was inserted into the test-tube and Blood was drawn to the zero mark with the aid of a rubber sucker. The filled ESR tube was allowed to stand vertically on the ESR stand for 1 hour. The area where the plasma stopped after 1 hour was read off as ESR and the result recorded accordingly (Ezeugwunne et al., 2012).
ESR is raised in a wide range of infectious, inflammatory, degenerative and malignant conditions associated with changes in plasma proteins, particularly increase in fibrinogen, immunoglobins and C-reactive protein.
The ESR increases with age and is higher in women than in men. The reference ranges that have been established and traditionally used reflect the effects of age and sex.
The higher limits of the reference range for the ESR in men and women 50 years or younger are 15 and 20 mm/h, respectively, whereas they are 20 and 30 mm/h, respectively, for men and women older than 50 years. These ranges have been confirmed to be applicable to our population using the Sediplast (Polymedco, Cortlandt Manor, NY) Westergren method and were used as the reference ranges for the current validation study (Bharathi et al., 2011).