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Management of patients with sickle cell anemia revolves around prevention of complications and aggressive treatment if they occur. For children, prophylactic antibiotics and pneumococcal vaccines are encouraged, as well as stroke prevention techniques already outlined. Patients may need transfusions every 3 to 5 weeks to maintain a hemoglobin of 9 to 11 g/dL and a hemoglobin S concentration of less than 50%,4 optimum standards to avoid complications. While a worthy goal, this treatment may lead to iron overload and the development of alloantibodies that could make future transfusions difficult. Both of these occurrences need to be carefully monitored by laboratory screening. Serum ferritin levels and antibody screening should be done routinely on this patient group. Perhaps one of the most auspicious developments for sickle cell patients was use of the drug hydroxyurea. Hydroxyurea increases the level of hemoglobin F in sickle cells, thereby reducing vaso-occlusive episodes and dramatically improving clinical outlooks in this patient group. First proposed by Samuel Charache in 1995, hydrox-yurea was found to be successful in reducing crisis intervals and acute chest syndrome at a reasonable drug dose and with few reversible side effects.24 This was a major breakthrough for this needy patient group and the multicenter clinical study was halted earlier than usual to offer this promising drug to more patients. At long last, sickle cell patients had a reason to be optimistic about their future. An additional, albeit more complex treatment is bone marrow transplantation from a well sibling or allogeneic match. Limited studies have suggested this as a viable alternative, but the procedure itself has considerable risks.

Patients with sickle cell anemia have considerable needs on multiple levels. For this reason, a thoughtful management plan should be developed and attended to so that this patient group may maximize their quality of life. Table 8.2 is presented as a table of interest for the reader. Additional help and advocacy can be obtained from the Sickle Cell Disease Association of America (www.sicklecelldisease.org) located in Baltimore, Maryland.

Laboratory Diagnosis

Patients with sickle cell anemia will have a lifelong nor-mochromic, normocytic anemia with decreased hemoglobin (between 6 and 8 g/dL), hematocrit, and red cell count. The reticulocyte count is always elevated leading to a slightly increased MCV in many cases. Bilirubin and LDH are increased, while haptoglobin is decreased, indicating extravascular hemolysis. During crisis

118 Part II • Red Cell Disorders

Table 8.2 O Clinical Management Scheme for the Sickle Cell Patient

Set 1: 0 to 5 years monitor for

Penicillin prophylaxis Splenic sequestration Fever or infection Stroke Pain

Dental care Complete blood count Red cell antigen typing Pneumococcal vaccine Set 2: 5 to 10 years monitor for Pain

Dental care

Add urinalysis and liver function test to lab Pulmonary function Chest radiograph Ultrasound

Ophthalmologic examination Set 3:10 years and beyond

Include all from Set 2 Family planning/self-help groups Leg ulcers episodes, the peripheral smear will show marked poly-chromasia, many nRBCs, target cells, and the presence of irreversible and reversible sickle cells (Fig. 8.2). Peripheral smears from sickle cell patients not in crisis show minimal changes, a few oat-shaped reversible sickle cells, and some polychromasia (Fig. 8.3). White cell counts may need to be corrected for nRBCs by applying the correction formula if automated instrumentation lacks this correction function (Fig. 8.4).

First-level screening procedures for adults include the dithionite solubility, a solubility test based on the principle that hemoglobin S precipitates in high-molarity buffered phosphate solutions. The amount of hemoglobin S is insignificant in this screening procedure because the purpose of this procedure is to detect the presence of hemoglobin S in the test sample. The end point is easy to read as a turbid solution in the presence of hemoglobin S and a clear solution if hemoglobin S is not present (Fig. 8.5). Newborn screening for hemo-globinopathies occurs in most states and for all ethnic groups in the United States, and provides the opportunity for early diagnosis and intervention for sickle cell anemia patients, key ingredients for successful disease

Figure 8.2 Irreversibly sickled cells. Note one pointed projection.

management. Most newborn blood samples are obtained by heel stick and the blood is applied onto dried filter paper ready to be processed for analysis, but cord blood samples are also acceptable. The samples are then analyzed by hemoglobin electrophoresis at either alkaline or acid pH or both, isoelectric focusing, or high-performance liquid chromatography. If elec-trophoretic techniques are used, two bands, hemoglobin F and hemoglobin S, will be seen in patients with sickle cell anemia because hemoglobin F is predominant in neonates. The healthy neonate will show two bands at hemoglobin A and hemoglobin F, while the individual with sickle cell trait will show three bands: one at F, one at A, and one at S. Table 8.3 shows the relative concentration of hemoglobins A and F at different ages. Challenges in neonatal screening involve identifying unexpected bands as well as small amounts of hemoglobin A or S.25

Figure 8.3 Reversible sickle cell. Note the blunted ends of the sickle cell.

Correct white count = original white count 100 + nRBCs x100

Figure 8.4 White cell corrections based on number of nRBCs.

Hemoglobin Electrophoresis

Hemoglobin electrophoresis is a time-honored quantitative procedure for isolating hemoglobin bands. This technique is based on the principle that hemoglobins migrate at different positions depending on pH, time of migration, and media used. Cellulose acetate and citrate agar are the media most often selected. Hemoglobin is isolated from a patient sample using a variety of lysing agents such as saponin or water. A small amount of sample is applied to the media and electrophoresed for the prescribed amount of time, and then each band is quantified using densitometry. Figure 8.6 is a comparison of cellulose acetate and citrate agar electrophoresis. What will become immediately noticeable for both media is that several bands have the same migration point. In analyzing each group of patterns, several features must be kept in mind to properly identify the abnormal hemoglobin (Table 8.4). On cellulose acetate at alkaline electrophoresis, hemoglobins E, C, OArab, and A2 migrate in the same position and hemoglobins S, D, and G travel together. On citrate agar at acid pH, hemoglobins A, O, A2, D, G, and E migrate to the same point. Yet, this medium provides excellent separation for hemoglobins S and D and hemoglobins C from E. In practice, most laboratories use a screening technique followed by a known quantitative method that has been

Figure 8.5 Sickle solubility test. An insoluble solution indicates the presence of Hemoglobin S. Clear solution is from a normal patient.

Table 8.3 O

Normal Hemoglobin A and Hemoglobin F Concentrations by Age

Age

Hgb F (%)

Hgb A (%)

1 day

77.0 ± 7.3

23 ± 7.3

Up to 12 months

1.6 ± 1.0

98.4 ± 1.0

Adult

<2.0

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