Sickling tests

Sickling tests are useful in confirming the presence of Hb S in a sample following initial electrophoresis at alkaline pH. When fuUy oxygenated Hb S is fully soluble but when deoxy-genated, polymerization occurs, forming insoluble tactoids, which deform the red cells in a characteristic rigid sickle... 

Electrophoresis (Figure 31-10) at both alkaline and acid pH shows bands in the S and C positions, and the sickling test is positive. 

Sickling test (metabisulfite test, which can t tell sickle cell disease from sickle cell trait)... 

Sickle test (African/Caribbean/Eastern Mediterranean descent)... 

Hematological Methods. Hematological analyses can Include the determination of the total hemoglobin concentration (In g%), the packed cell volume (PCV In %), the red blood cell count (In 10 /mm ) and reticulocytes count (In %), calculation of the red cell Indices, examination of a blood film, tests to demonstrate the presence of Inclusion bodies and of sickle cells, tests to evaluate the distribution of fetal hemoglobin (Hb-F) Inside the red cells, the red cell osmotic fragility, the concentration of serum Iron (SI), total Iron binding capacity (TIBC), and the survival time of the red cells. Details of all... 

UicAochAornatogAoptiic TcAtcng MetkodA ioA Sickle, Cell Anemia and Related Vl60AdeAA in the AdixJit. The procedures described in the preceding Section are, in fact, applicable to the detection of hemoglobinopathies in the adult, and any quantitative determination of Hb-A2 immediately becomes a qualitative test for abnormal Hb s. If, instead of the very small zone of Hb-A2, a prominent zone moves in the same way, Hb-C (or Hb- ) is indicated. 

CoAd Blood Testing oa Sickle Cell Anemia and Related Vl6-oAdeAS by AlienachAomatogAaphlc Methods. The CM-Sephadex procedure easily detects Hb-S and Hb-C at birth but the diffuse zone of Hb-A has on occasion been difficult to see. Substitution of CM-Cellulose for CM-Sephadex has yielded a superior mlcrochromatographlc method, and the compact, well-defined zones of the CM-Cellulose column facilitate the Interpretation of the results even though the amount of sample Is only 20% as great. The CM-Cellulose method Is as simple and rapid as the original CM-Sephadex procedure (27. 28). 

Class II devices are those for which general controls alone are insufficient to provide reasonable assurance of safety and effectiveness and for which sufficient information is available to establish special controls to provide this assurance. Special controls may include performance standards, postmarket surveillance, and guidance for analytical/clinical data. Examples of class II IVDs are automated differential cell counters, fetal hemoglobin test systems, sickle-cell tests, and Toxoplasma gondii serological reagents. 

Direct tests have been applied to sickle-cell disease, thalassemia, and hemophilia A and have documented this great genetic diversity. About 100 defective gene sites have been identified for thalassemia, and there may be more than 1000 associated with the factor VIII gene. 

Example Restriction site polymorphism for Msfll may be used to identify individuals with the sickle ceil mutation (see Chapter 7, Genetic Testing). 

PCR Testing for Sickle Cell Disease with ASO Probes... 

A man with sickle cell disease and his phenotypically normal wife request genetic testing because they are concerned about the risk for their unborn child. DNA samples from the man and the woman and from fetal cells obtained by amniocentesis are analyzed using the PCR to amplify exon 1 of the p-globin gene. 

A couple is expecting their first child and have consulted a genetic coun or because the woman had a brother who died of sickle cell anemia. There is also a history of disease in the man s family. Fetal cells are obtained by amniocentesis. Which test would best determine whether the fetus would be born with the disease ... 

For idiosyncratic, patient related adverse reactions, less confirmatory tests are available but the number is growing. Skin, blood and urine tests are available to confirm acute and chronic allergic reactions. Genetic tests can determine the susceptibility of individuals and includes general tests such as for the porphyrias and sickle cell anaemia, and specific tests for dmg metabolism, such as acetylator status... 

Other Interferent Studies with Nylon Filters. Retention of HONO on Gelman Nylasorb (nylon 6) filters was tested 0.3 to 1 xg/m3 HONO was sampled in air (—50% RH) at 20 L/min with 47-mm filters for 16-23 h. At saturation, the filters contained 1.8 xg/cm2 N02 this result indicates less than 50% efficiency for HONO retention (19). Sampling 440 xg/m3 HONO at 20 L/min with 47-mm Gelman Nylasorb filters (nylon type unstated), Sickles and Hodson reported about 25% retention efficiency, with a similar saturation value, and noted that such retention was reversible. Substantial oxidation of HONO to N03 on the filter surface by 03 was demonstrated in laboratory and atmospheric trials (21). Perrino et al. (20) observed with 47-mm Gelman Nylasorb (nylon type unstated) filters an efficiency for HONO that increased from about 25 to about 90% as the flow rate decreased from 12 to 2 L/min, with saturation at —50 xg/filter. Nitrite to nitrate conversion on the nylon filter surface increased from 13% at 45 ppb 03 to 93% at 200 ppb 03. 

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