Sten Öhman

Reference values for CSF-IgM, CSF-IgM/S-IgM ratio and IgM index, and its application to patients with multiple sclerosis and aseptic meningoencephalitis

Immunoglobulin M (IgM) concentrations were determined in cerebrospinal fluid (CSF) and serum (S) by enzyme-linked immunosorbent assay (ELISA). In 52 reference subjects, the upper reference limit was 0.46 mg/l for CSF-IgM, 0.32 X 10(-3) for CSF-IgM/S-IgM ratio, and 0.061 for IgM index equal to CSF-IgM X S-albumin/S-IgM X CSF-albumin ratio. No correlation to age over 15-85 years was found for any of these variables. Among 22 patients with aseptic meningoencephalitis (AM) elevated values of CSF-IgM were found in 68%, CSF-IgM/S-IgM ratio in 73%, and IgM index in 73%. The corresponding values among 35 patients with multiple sclerosis (MS) were 66%, 60% and 63%. The differences in diagnostic sensitivities for the three IgM variables were not significant. Eleven of 16 AM patients and two of 22 with MS had elevated IgM index in the presence of normal IgG and IgA indices. Determination of IgM index should therefore be performed in suspected inflammatory nervous system disorders.

Comparison of Seven Formulae and Isoelectrofocusing for Determination of Intrathecally Produced IgG in Neurological Diseases

Seven different formulae and agarose isoelectrofocusing (AIF) using immunolabelling for IgG were compared for their ability to discriminate between intrathecally produced IgG and transudated IgG in cerebrospinal fluid. All reference limits were set to a specificity of 97·5% (reference group, n = 211). The probability of a positive test (p +) was evaluated for 112 patients with multiple sclerosis (MS), 42 with meningitis, 114 with noninflammatory diseases affecting the central nervous system (CNS), 23 with Guillain-Barré syndrome, and 56 with various diseases not affecting the CNS. Agarose isoelectrofocusing had the best diagnostic sensitivity (93%) for MS, combined with a low p + (0–19%) for other diseases. Among the formulae, the IgG extended index and Reibers hyperbolic formula were equivalent, giving high (75–79%) diagnostic sensitivity for MS combined with low p + (4–22%) for other diseases. All other formulae, although sensitive for MS, had a higher rate of false positive results.

A method for quantitative wet chemical analysis of urinary calculi

We describe a simple method for quantitative chemical analysis of urinary calculi requiring no specialized equipment. Pulverized calculi are dried over silica gel at room temperature and dissolved in nitric acid, which was the only effective agent for complete dissolution. Calcium, magnesium, ammonium, and phosphate are then determined by conventional methods. Oxalate is determined by a method based on the quenching action of oxalate on the fluorescence of a zirconium-flavonol complex. Uric acid, when treated with nitric acid, is stoichiometrically converted to alloxan, which is determined fluorimetrically with 1,2-phenylenediamine. Similarly, cystine is oxidized by nitric acid to sulfate, which is determined turbidimetrically as barium sulfate. Protein is determined spectrophotometrically as xanthoprotein. The total mass recovery of authentic calculi was 92.2 +/- 6.7 (SD) per cent. The method permits analysis of calculi as small as 1.0 mg. Internal quality control is performed with specially designed control samples.

Improved formulae for the judgement of intrathecally produced IgA and IgM in the presence of blood CSF barrier damage.

In order to discriminate between transsudated and intrathecally produced IgA and IgM in patients with blood cerebrospinal fluid (CSF) barrier (BCB) damage, we developed extended indices (IgA-EI and IgM-EI) for these immunoglobulins according to the general formula for extended index of a component X in CSF: where a is a parameter specific for X. For IgA parameter a was found to be 1·15 and for IgM 1·9. A preliminary evaluation of IgA-EI and IgM-EI indicated lower false positive rates as compared to CSF IgA and IgM concentrations as well as ‘conventional’ IgA and IgM indices in cases with BCB damage, and essentially the same rates as for the hyperbolic formulae of Reiber and Felgenhauer. The importance of reliable sampling and analytical technique for IgM in CSF is discussed.

Serum calcium ion activity. Some aspects on methodological differences and intraindividual variation.

Sera were analyzed for calcium ion activity on the Orion 99-20 and SS-20 systems. Samples from 84 healthy subjects were analyzed on both systems and, because of a change of electrode composition, 74 of them were reanalyzed after this change. Additional 89 were analyzed on only SS-20. The distribution of serum calcium ion activity was close to Gaussian. The difference between the 99-20 and SS-20 readings was 0.048+/-0.017 mmol/liter (range -0.01 to 0.08) before the electrode change and -0.085+/-0.027 mmol/liter (range -0.14 to 0.02) after. The reference ranges were 1.02--1.23 mmol/liter for 99-20 and 0.93--1.20 mmol/liter for SS-20 before the electrode change. The following characteristics may contribute to differences in the readings: higher temperature, higher flow rate, new calcium and reference electrodes, new liquid junction construction and a new pumping procedure. For 74 subjects the determination of serum calcium ion activity (99-20 system) was performed with a five year interval and the difference between the first and second measurements was -0.0046+/-0.0168 mmol/liter (mean +/-SD), ranging from -0.04 to 0.03 mmol/liter. This corresponded to an intraindividual variation of 1.5%. The corresponding variations for serum total calcium and corrected calcium were 4.8% and 3.3% respectively.

Evaluation of Radiometer ICA1 as a routine instrument for serum ionized calcium and its application for whole blood capillary samples from newborn infants

The Radiometer ICA1 was evaluated with four sets of samples: a) 289 serum samples sent for routine analysis of ionized calcium, b) a reference set of serum samples from 40 healthy laboratory workers, c) 42 capillary whole blood samples from healthy full-term and d) six capillary whole blood samples from pre-term infants. For comparison, all sets except the capillary samples were also run on the Orion SS-20. The ICA1 gave higher readings than the Orion SS-20 for normo-(mean difference 0.011 mmol/l) and hypocalcaemic (mean difference 0.037 mmol/l), but not for hypercalcaemic serum samples. The mean +/- 2 SD range for the serum reference set was 1.15-1.31 mmol/l for ICA1 and 1.14-1.27 mmol/l for Orion SS-20. The within-assay and between-assay precision were 0.014 and 0.032 mmol/l (SD) respectively for ICA1 and 0.010 and 0.022 mmol/l (SD) for Orion SS-20. The 42 healthy full-term infants had a mean +/- 2 SD range of 1.18-1.47 mmol/l. The six pre-term infants had whole blood ionized calcium 0.82-1.07 mmol/l. Three of them had ionized calcium less than 0.90 mmol/l and a symptomatic hypocalcemia.

Clinical Significance of Phosphate in Calcium Oxalate Renal Stones

We analysed calcium, magnesium, oxalate, citrate, urate and creatinine in urine and calculated risk factors in patients who had formed stones composed of calcium oxalate, and calcium phosphate, alone or as a mixture. Patients producing pure calcium oxalate stones (< 0·1% phosphate) had a higher oxalate, and lower calcium excretion than stone-free subjects and patients forming other stone types. In contrast, patients producing calcium oxalate stones containing phosphate, even in trace amounts (> 0·1%) had no increase in oxalate excretion, but a higher calcium excretion than stone-free subjects. We could not correlate any computed variable (e.g. AP(CaOx) index) to stone composition. We conclude that pure CaOx stones may be the result of a high oxalate excretion, and that other calcium containing stones may have another and probably more complex aetiology, including primary precipitation of calcium phosphates.

Lower Values for Immunoglobulin M in Cerebrospinal Fluid When Sampled with an Atraumatic Sprotte Needle Compared with Conventional Lumbar Puncture

Immunoglobulin M (IgM) has a very low concentration in cerebrospinal fluid (CSF) compared with serum, and therefore determinations of IgM in CSF are highly sensitive to pre-analytical errors caused by contamination with serum or interstitial fluid. Capillary attraction causes a thin layer of liquid containing serum proteins to be formed inside a conventional (Quincke) needle during penetration of tissue. To investigate this source of pre-analytical error, 35 patients had lumbar punctures using a 22 G atraumatic (Sprotte) or 25 G conventional (Quincke) needle according to a randomized scheme, and the IgM concentrations in CSF and serum were determined. The CSF IgM concentrations for samples taken with a Sprotte needle were significantly lower than those taken with a Quincke needle (P < 0·05), whereas the corresponding serum IgM concentrations and CSF erythrocyte counts did not differ significantly. The difference indicates that CSF IgM concentrations determined after conventional sampling may be falsely increased by contamination. We conclude that IgM concentrations in CSF samples taken with the atraumatic technique are more accurate, and recommend the use of this technique when CSF IgM is to be determined.

Determination of Total and Herpes Simplex Virus Specific Monomeric and Dimeric IgA in Serum and Cerebrospinal Fluid by Ultracentrifugation

An improved method is described for differentiating between monomeric and dimeric total and herpes simplex virus (HSV) specific IgA by ultracentrifugation in sucrose gradient, using recovery and quantitative analysis of the fractions obtained. Calculation of monomeric and dimeric IgA was based on IgG as an internal standard. Intrathecally produced monomeric and dimeric IgA were judged by calculating IgA indices for each form. A new type of formula indicating relative over-production of dimeric compared with monomeric IgA (IgA dimeric-monomeric index) is suggested. The method was applied to serum and cerebrospinal fluid (CSF) from three patients with HSV encephalitis. The index for monomeric as well as dimeric IgA was high during the acute phase of the disease, indicating intrathecal synthesis of both molecular forms. One year after onset, there was no detectable HSV-specific IgA in CSF: Both molecular forms, however, remained in serum. The amount of dimeric compared with monomeric IgA was high during the acute phase, and subsequently decreased after successful treatment. A new finding was the detection of HSV-specific IgA heavier than dimeric IgA in serum one year after onset of the disease. These components may be tetrameric IgA, or immune complexes containing IgA.

What is Renal Stone Matrix

The interest concerning the composition of urinary calculi has been focused on the crystalline components since these constitute a major part of the stone. Important studies of organic matrix have been carried out by Boyce and King (1). In immunological experiments, they found mucoproteins to be present both in stones and in urine. Since then, the “matrix” has been considered to consist of mucoproteins. However, mucoproteins represent less than 3% of the stone weight, whereas the organic matter approximates 10–20% (1–3).