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The National Bone Health Alliance (NBHA) recommends standardized sample handling and patient preparation for C-terminal telopeptide of type I collagen (CTX-I) and N-terminal propeptide of type I procollagen (PINP) measurements to reduce pre-analytical variability. Controllable and uncontrollable patient-related factors are reviewed to facilitate interpretation and minimize pre-analytical variability. INTRODUCTION: The IOF and the International Federation of Clinical Chemistry (IFCC) Bone Marker Standards Working Group have identified PINP and CTX-I in blood to be the reference markers of bone turnover for the fracture risk prediction and monitoring of osteoporosis treatment. Although used in clinical research for many years, bone turnover markers (BTM) have not been widely adopted in clinical practice primarily due to their poor within-subject and between-lab reproducibility. The NBHA Bone Turnover Marker Project team aim to reduce pre-analytical variability of CTX-I and PINP measurements through standardized sample handling and patient preparation. METHODS: Recommendations for sample handling and patient preparations were made based on review of available publications and pragmatic considerations to reduce pre-analytical variability. Controllable and un-controllable patient-related factors were reviewed to facilitate interpretation and sample collection. RESULTS: Samples for CTX-I must be collected consistently in the morning hours in the fasted state. EDTA plasma is preferred for CTX-I for its greater sample stability. Sample collection conditions for PINP are less critical as PINP has minimal circadian variability and is not affected by food intake. Sample stability limits should be observed. The uncontrollable aspects (age, sex, pregnancy, immobility, recent fracture, co-morbidities, anti-osteoporotic drugs, other medications) should be considered in BTM interpretation. CONCLUSION: Adopting standardized sample handling and patient preparation procedures will significantly reduce controllable pre-analytical variability. The successful adoption of such recommendations necessitates the close collaboration of various stakeholders at the global stage, including the laboratories, the medical community, the reagent manufacturers and the regulatory agencies.

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Bone turnover markers are subject to day-to-day and within-day variability, which may influence clinical interpretation. We examined the effect of fasting vs. feeding on the concentration and between-day variability of several markers. Twenty healthy premenopausal women were studied on 10 consecutive weekdays. Subjects were studied either in the fasting (no breakfast) or fed (breakfast at 08:00 h) state on alternate days, and were randomized to begin either fasting or fed. Two hour urine collections were obtained each day between 08:00 h and 10:00 h, and blood samples were collected daily at 09:00 h. The N-telopeptide cross-link of type I collagen in urine (uNTX) and serum (sNTX), the C-telopeptide in urine (uCTX) and serum (sbetaCTX), and immunoreactive free deoxypyridinoline (uifDPD) in urine were measured as resorption markers. Procollagen type I N-terminal propeptide (PINP), osteocalcin (OC), and bone alkaline phosphatase (bone ALP) were measured as formation markers. All bone formation and resorption markers were significantly lower in the fed state with the exception of bone ALP. The magnitude of the decrease ranged from 3.8 +/- 0.9% for PINP (p < 0.0001) to 17.8 +/- 2.6% (p < 0.0001) for sbetaCTX. Measurement variability was partitioned into analytical variability based on replicate assays (CV(a)) and within-subject variability (CV(i)). The CV(i) was greater (p < 0.05) for some markers in the fasting state (uifDPD, uNTX, and sNTX) but greater in the fed state for other markers (OC and sbetaCTX). In conclusion, the clinical impact of feeding vs. fasting is small with the exception of sbetaCTX; however, in clinical practice, collection of samples in the fasting state may be necessary to minimize the unpredictable effects of feeding. The mechanism of the acute effect of feeding on bone turnover remains uncertain.

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Cerebrospinal fluid (CSF) myelin basic protein (MBP) was measured blind by double antibody competitive inhibition radioimmunoassay (RIA) in 20 children who had seizures and 17 children with hydrocephalus. MBP values correlated with clinical outcome and mean maximum intracranial pressure (ICP) in the hydrocephalic group, and with type of convulsion in the epileptic group. A value of 20ng/ml or more was regarded as significantly raised. A significant rise in MBP levels could be demonstrated in those with ICP alone and in patients with additional problems, whose levels tended to be even higher. Hydrocephalic children with normal ICP and children with seizures had similar normal MBP levels, and in the latter group clinical outcome was not related to MBP levels. For individual patients CSF MBP is of little value as a prognostic indicator, or as a method of quantifying cerebral damage.

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Concentrations of seven neuropeptides have been determined in 69 human neurological tumours. The majority of tumours were intrinsic to the central nervous system, being astrocytomas. In general, within the the better differentiated tumours (Grade I/II astrocytomas) higher concentrations of five neuropeptides (neuropeptide Y, somatostatin, substance P, vasoactive intestinal peptide and cholecystokinin) were measured in comparison to the poorly differentiated tumours. Of the metastatic tumours, five were derived from oat cell carcinoma of the bronchus. Very high concentrations of bombesin were identified in these metastases.

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In 44 patients undergoing neurosurgical procedures for intracranial tumors, subarachnoid hemorrhage, or spinal and peripheral nerve lesions, serum myelin basic protein (MBP) immunoreactivity was measured preoperatively and serially in the first 10 postoperative days. The double-antibody radioimmunoassay method was used, with a detection limit of 2.5 ng/ml in serum. Clinical evaluation was carried out at admission and on successive days during the period of neurosurgical management; outcome was assessed later. In the early postoperative phase, there was a fall in MBP immunoreactivity in all groups of patients. In the groups with intracranial tumor and subarachnoid hemorrhage, there was a subsequent rise in MBP immunoreactivity before the end of the 10-day period, which was not found in the group with spinal and peripheral nerve lesions.

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A sensitive radioimmunoassay that can detect brain damage in cases of head injury and stroke was applied to blood samples from 13 patients before and after they received multiple treatments with electroconvulsive therapy for psychiatric disorder. None of the patients showed a significant increase in serum myelin basic protein immunoreactivity. As increased serum myelin basic protein immunoreactivity may reflect myelin damage it is apparent that in these patients electroconvulsive therapy did not cause measureable breakdown of myelin.

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Patients admitted to the neurosurgical wards for the management of nervous system tumours, subarachnoid and intracerebral haemorrhage, head injury, spinal and peripheral nerve lesions, and other miscellaneous neurosurgical conditions, were studied by assay of serum immunoreactivity for myelin basic protein. Of 171 patients, 70% proved to have elevated myelin basic protein activity. In cerebral cases the extent of brain damage assessed by clinical methods appeared to correlate with the appearance of elevated serum myelin basic protein. In spinal and peripheral nerve cases no similar elevation of myelin basic protein was observed.

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46 patients treated by operative neurosurgery for spontaneous subarachnoid haemorrhage, intracranial tumour and spinal diseases were studied. Levels of circulating immunoglobulin and complement were measured pre-operatively and serially in the first 10 post-operative days. Prior to operation immunoglobulin levels in all categories of patients were distributed normally. However, immediately post-operatively IgG and IgM fell sharply. Conversely IgA rose in a marked manner and C3 levels showed a gradual increase. Later, antibody levels tended to return to normal.

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Forty three patients, admitted to the department of Neurological Surgery for management of central nervous system tumours, were studied pre-operatively for serum myelin basic protein immunoreactivity as a marker of central nervous system lesion and for circulating immunoglobulins and complement (C3) levels. Myelin basic protein concentration did not appear to correlate with tumour type or grade. Serum immunoglobulin levels were found to be within the normal range but the mean IgM level was significantly higher in the glioma group when compared with meningiomas.

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Leucocyte migration inhibition in response to ubiquitous antigens was studied in 104 patients as an in vitro indicator of cell-mediated immunity. Patients with cerebral glioma, benign intracranial tumours, and subarachnoid haemorrhage demonstrated impaired inhibition of leucocyte migration compared with control subjects. The greatest impairment occurred in patients with subarachnoid haemorrhage, while the least impairment was seen in patients with glioma. Significant rises in inhibition of leucocyte migration in response to antigen preparations from glioma and normal brain were seen in the early post-operative period in patients with glioma and subarachnoid haemorrhage. Impaired cellular immunity, together with sensitivity of lymphocytes to brain-derived antigens, are features of cerebral disease in general and not specific for glioma.

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