Untersuchungen zur differenzialdiagnostischen Bedeutung des IgG-Index und Albuminquotienten bei neurologisch erkrankten Hunden
Investigation of IgG index and albumin quotient for the differential diagnosis of dogs with neurological diseases In the present study the benefit of IgG index and albumin quotient for the differential diagnosis in dogs with neurological diseases was investigated. The question whether the determination of these two parameters is a convenient extension of the conventional cerebrospinal fluid (CSF) examination was explored. The IgG index served as an indicator for intrathecal IgG synthesis, the albumin quotient as an indicator for disturbances in the blood-brain barrier. The concentrations of albumin and IgG in CSF and serum of 122 dogs were determined with the help of nephelometry, followed by the calculation of the albumin quotient and IgG index. The conventional CSF examination included cell count, cell morphology, Pandy’s test, and protein content. All 122 dogs could be categorized into five different groups according to the clinical and pathological findings: inflammatory diseases (n = 33), tumors (n = 11), disc prolaps (n = 37), orthopedic diseases (n = 20), and idiopathic epilepsy (n = 21). In 10% of the examined dogs (12 of 122), pathological findings of the cerebrospinal fluid could only be exposed with the help of IgG index or albumin quotient, with the total protein level being normal. This result was equivalent to 14% of the dogs with normal total protein levels. Among these patients were dogs with white dog shaker disease, distemper, steroid responsive meningitis arteritis, and plexus carcinoma. On the other side, dogs with increased CSF total protein had a 97% chance of increased IgG index or albumin quotient. 67% of the dogs with inflammatory diseases showed an increase in IgG index and 70% an increase in albumin quotient. In 46% of these animals both parameters were elevated. Maximum changes were observed in dogs with central European tick-borne encephalitis. Dogs with white dog shaker disease were the only ones to exhibit an exclusive increase in the IgG index. 36% of the patients with tumors showed an increase in IgG index and 64% an increase in albumin quotient. In 18% of the animals both parameters were elevated. The highest level of all IgG indices was obtained in a patient with an ependymoma. Patients with disc prolapse showed in 8% of the cases a mild increase in IgG index and in 14% a mild increase in albumin quotient, but never a combination of both. In dogs with orthopedic diseases, two (10%) had a slight increase in CSF total protein and albumin quotient, which could not be explained with the orthopedic findings and which indicated an additional neurological disease. As expected, no changes occurred with idiopathic epilepsy. Even when there were highly significant differences between the single groups of patients, one group never differed significantly from all of the others groups in both parameters – neither in absolute levels nor in the proportion of altered values. In dogs with neurological symptoms without increased levels of protein, IgG index and albumin quotient can help to identify pathological findings of the cerebrospinal fluid. In the future, the determination of IgG index and albumin quotient will be an useful extension of the routinely used CSF examination in dogs with neurological diseases.
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