Question

which of the following test is evaluted by using Coulter counter method ?




leakage test
pyrogen test
clarity test
sternity test​

Answer 1

Answer:

☆2.1 Particle Counter

2.1.1 Conductivity Counters (Rosse and Loizeau, 2003; Beyer, 1987)

Conductivity (Coulter) counters consist of two chambers. Nanoparticles are suspended in an electrolyte solution and placed in the sample chamber, while an electrolyte alone is placed in a reference chamber. Then, the nanoparticle solution passes through the electrolyte solution. As the nanoparticle solution passes through the electrolyte solution, a change in conductivity occurs and is measured. The difference in conductivity is a function of the particle size.

2.1.2 Condensation Particle Counters

In this method, nanoparticles are drawn in an aerosol sample continuously through a heated saturator. Inside, alcohol or water is vaporized and the vapor diffuses into the sample stream. The aerosol sample saturated with the liquid vapor becomes supersaturated and ready to condense. Nanoparticles serve as a condensation area for the vapor; thus, they grow in size as their optical density is recorded.

The advantages of counting methods include measurement of true volume distribution and high resolution and a wide range of sample measurements. The disadvantages include a need for calibration, use of electrolyte as the medium (limited to hydrophilic particles), and low-particle concentration. In addition, errors may occur with porous particles, particles below the minimum detectable size go unnoticed, and there is difficulty with high-density materials.

☆Investigations

A complete blood count and reticulocyte count should be obtained with every painful crisis because of possible associated aplastic crisis. Aplastic crisis can be caused by concomitant parvovirus infection. Determination of white blood cell counts by Coulter counter methods should always be followed by a corrected white blood cell count because any immature nucleated red blood cells detected are read as leukocytes. An increasing erythrocyte sedimentation rate (ESR) and leukocytosis with a left differential shift suggest local or systemic infection, possibly osteomyelitis. In uncomplicated SS patients the ESR is usually low because of the unique rheology of sickled red blood cells, but it may rise during the resolving phase of the painful crisis and to a greater extent if infection is present. Determination of C-reactive protein is more reliable than the ESR when monitoring an inflammatory process.

No radiographic changes are typical of uncomplicated painful crises, but periosteal reaction can be seen. Blood cultures should be performed if the patient's temperature exceeds 38° C. Joint aspiration is necessary for painful crisis with associated arthritis. In uncomplicated arthritis, the synovial fluid is noninflammatory, straw colored, and sterile. Blood cultures are always indicated for dactylitis because Salmonella infections have been documented in patients with this complication.18

Radiographs of affected bones are not helpful in the early stages of osteomyelitis, and such changes are apparent only after weeks of illness. Plain radiographs and bone scans are unable to differentiate between painful crises and osteomyelitis. At present, soft tissue ultrasound and gadolinium-enhanced MRI are the best imaging techniques to suggest bone infection, although the exact specificity of these investigations is not yet clear. With ultrasound, a 4-mm depth or more of subperiosteal fluid is highly suggestive of osteomyelitis.19 On gadolinium-enhanced MRI, acute infarcts demonstrate thin, linear rim enhancement, whereas osteomyelitis shows more geographic and irregular marrow enhancement.20 Patients with osteonecrosis of the femoral head can be staged radiographically by the Steinberg classification system.21 In the early stages findings on plain radiographs are normal, but the hip is symptomatic with groin or thigh pain, which is worse at night (Steinberg stage 1). However, MRI can detect abnormalities at this stage, even where bone scans fail. Because of an overall reported sensitivity of 91%, MRI should be performed if avascular necrosis is suspected. Stage 2 hips show sclerosis and radiolucent areas on radiographs (Fig. 195.5), with the symptoms being similar to those in stage 1. In stage 3, plain films show a lucent subchondral line, followed by a cortical discontinuity (crescent sign); it appears only after several weeks of illness. At this stage the pain and limitation have increased and ambulation may be possible only with a cane. Stage 4 is characterized by segmental flattening of the femoral head without radiologic evidence of acetabular involvement (Fig. 195.6). Stage 5 shows progressive destruction of the hip joint with joint space narrowing, cyst sclerosis, and osteophytes (Fig. 195.7). Stage 6 includes advanced degenerative joint disease with extreme narrowing or obliteration of the joint space. It is important to recognize that correla­tion between the clinical symptoms and radiologic features of osteonecrosis is poor.