Reference intervals for CTX and P1NP in a multi-ethnic Malaysian cohort

BACKGROUND

Well defined reference intervals are central to the utility of serum C-terminal telopeptide of type 1 collagen (CTX) and N-terminal propeptide of type I procollagen (P1NP), designated as reference markers in osteoporosis, and useful for monitoring therapeutic response in that condition. This study reports the reference intervals for plasma CTX and serum P1NP in a multi-ethnic Malaysian population.

METHODS

Ethnic Malay, Chinese or Indian subjects aged 45-90 years old were recruited from Selangor, Malaysia from June 2016 to August 2018. Subjects with known medical conditions (e.g., bone disorders, malnutrition, immobilisation, renal impairment, hormonal disorders) and medications (including regular calcium or vitamin D supplements) that may affect CTX and P1NP were excluded. Additionally, subjects with osteoporosis or fracture on imaging studies were excluded. The blood samples were collected between 8 a.m. and 9 a.m. in fasting state. The CTX and P1NP were measured on Roche e411 platform in batches.

RESULTS

The 2.5th-97.5th percentiles reference intervals (and bootstrapped 90%CI) for plasma CTX in men (n = 91) were 132 (94-175) - 775 (667-990) ng/L; in post-menopausal women (n = 132) 152 (134-177) - 1025 (834-1293) ng/L. The serum P1NP reference intervals in men were 23.7 (19.1-26.4) - 83.9 (74.0-105.0) µg/L, and in post-menopausal women, 25.9 (19.5-29.3) - 142.1 (104.7-229.7) µg/L.

CONCLUSION

The reference intervals for plasma CTX and serum PINP for older Malaysian men and post-menopausal women are somewhat different to other published studies from the region, emphasising the importance of establishing specific reference intervals for each population.

Correction to: A Multicenter Study to Evaluate Harmonization of Assays for C-Terminal Telopeptides of Type I Collagen (ß-CTX): A Report from the IFCC-IOF Committee for Bone Metabolism (C-BM)

A correction to this paper has been published: https://doi.org/10.1007/s00223-021-00839-y

A Multicenter Study to Evaluate Harmonization of Assays for C-Terminal Telopeptides of Type I Collagen (ß-CTX): A Report from the IFCC-IOF Committee for Bone Metabolism (C-BM)

BACKGROUND

Biochemical bone turnover markers are useful tools to assess bone remodeling. C-terminal telopeptide of type I collagen (ß-CTX) has been recommended as a reference marker for bone resorption in research studies.

METHODS

We describe the results of a multicenter study for routine clinical laboratory assays for ß-CTX in serum and plasma. Four centers (Athens GR, Copenhagen DK, Liege BE and Sheffield UK) collected serum and plasma (EDTA) samples from 796 patients presenting to osteoporosis clinics. Specimens were analyzed in duplicate with each of the available routine clinical laboratory methods according to the manufacturers' instructions. Passing-Bablok regressions, Bland-Altman plots, V-shape evaluation method, and Concordance correlation coefficient for ß-CTX values between serum and plasma specimens and between methods were used to determine the agreement between results. A generalized linear model was employed to identify possible variables that affected the relationship between the methods. Two pools of serum were finally prepared and sent to the four centers to be measured in 5-plicates on 5 consecutive days with the different methods.

RESULTS

We identified significant variations between methods and between centers although comparison results were generally more consistent in plasma compared to serum. We developed univariate linear regression equations to predict Roche Elecsys®, IDS-iSYS, or IDS ELISA ß-CTX results from any other assay and a multivariable model including the site of analysis, the age, and weight of the patient. The coefficients of determination (R²) increased from approximately 0.80 in the univariate model to approximately 0.90 in the multivariable one, with the site of analysis being the major contributing factor. Results observed on the pools also suggest that long-term storage could explain the difference observed with the different methods on serum.

CONCLUSION

Our results show large within- and between-assay variation for ß-CTX measurement, particularly in serum. Stability of the analyte could be one of the explanations. More studies should be undertaken to overcome this problem. Until harmonization is achieved, we recommend measuring ß-CTX by the same assay on EDTA plasma, especially for research purposes in large pharmacological trials where samples can be stored for long periods before they are assayed.

Clinical usefulness of bone turnover marker concentrations in osteoporosis

Current evidence continues to support the potential for bone turnover markers (BTM) to provide clinically useful information particularly for monitoring the efficacy of osteoporosis treatment. Many of the limitations identified earlier remain, principally in regard to the relationship between BTM and incident fractures. Important data are now available on reference interval values for CTX and PINP across a range of geographic regions and for individual clinical assays. An apparent lack of comparability between current clinical assays for CTX has become evident indicating the possible limitations of combining such data for meta-analyses. Harmonization of units for reporting serum/plasma CTX (ng/L) and PINP (μg/L) is recommended. The development of international collaborations continues with an important initiative to combine BTM results from clinical trials in osteoporosis in a meta-analysis and an assay harmonization program are likely to be beneficial. It is possible that knowledge derived from clinical studies can further enhance fracture risk estimation tools with inclusion of BTM together with other independent risk factors. Further data of the relationships between the clinical assays for CTX and PINP as well as physiological and pre-analytical factors contributing to variability in BTM concentrations are required.

Markers of bone turnover for the prediction of fracture risk and monitoring of osteoporosis treatment: a need for international reference standards

The International Osteoporosis Foundation (IOF) and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommend that a marker of bone formation (serum procollagen type I N propeptide, s-PINP) and a marker of bone resorption (serum C-terminal telopeptide of type I collagen, s-CTX) are used as reference analytes for bone turnover markers in clinical studies.

INTRODUCTION

Bone turnover markers (BTM) predict fracture risk, and treatment-induced changes in specific markers account for a substantial proportion of fracture risk reduction. The aims of this report were to determine their clinical potential in the prediction of fracture risk and for monitoring the treatment of osteoporosis and to set an appropriate research agenda.

METHODS

Evidence from prospective studies was gathered through literature review of the PUBMED database between the years 2000 and 2010 and the systematic review of the Agency for Healthcare Research and Quality up to 2001.

RESULTS

High levels of BTMs may predict fracture risk independently from bone mineral density in postmenopausal women. They have been used for this purpose in clinical practice for many years, but there is still a need for stronger evidence on which to base practice. BTMs provide pharmacodynamic information on the response to osteoporosis treatment, and as a result, they are widely used for monitoring treatment in the individual. However, their clinical value for monitoring is limited by inadequate appreciation of the sources of variability, by limited data for comparison of treatments using the same BTM and by inadequate quality control. IOF/IFCC recommend one bone formation marker (s-PINP) and one bone resorption marker (s-CTX) to be used as reference markers and measured by standardised assays in observational and intervention studies in order to compare the performance of alternatives and to enlarge the international experience of the application of markers to clinical medicine.

CONCLUSION

BTM hold promise in fracture risk prediction and for monitoring treatment. Uncertainties over their clinical use can be in part resolved by adopting international reference standards.

A randomized clinical trial comparing oral alendronate and intravenous pamidronate for the treatment of Paget's disease of bone

Second and third generation bisphosphonates are the treatment of choice for Paget's disease of bone. These drugs are more effective than calcitonin and etidronate, but there have been no head to head, randomized controlled trials comparing potent bisphosphonates. We conducted a 2-year, randomized, open-label trial comparing oral alendronate and intravenous pamidronate in 72 subjects with Paget's disease. Randomization was stratified according to baseline plasma total alkaline phosphatase (ALP) and previous bisphosphonate treatment (yes or no). All previously treated patients had received pamidronate but not alendronate. Assigned treatments were pamidronate (60 mg) every 3 months as a single infusion or alendronate (40 mg) daily in 3-month blocks, continued until biochemical remission (defined as both ALP and urine deoxypyridinoline (DPD)/creatinine ratio in the reference range) or a clear plateau effect was observed. At 1 year, nonresponders to pamidronate were crossed over to alendronate treatment. At 1 year, 31/36 (86%) subjects randomized to alendronate achieved biochemical remission compared with 21/36 (56%) for pamidronate (P = 0.017). There was a significantly greater reduction in ALP (P < 0.001) and DPD/creatinine ratio (P < 0.001) for alendronate compared with pamidronate treatment. In previously untreated patients, alendronate resulted in remission in 20/22 (91%) subjects compared with 19/22 (86%) of pamidronate-treated subjects, which was not significantly different; however, alendronate resulted in a significantly greater reduction in ALP (P = 0.014) and DPD/creatinine ratio (P < 0.001). In previously treated patients, alendronate resulted in remission in 11/14 (79%) subjects compared with 2/14 (14%) for pamidronate (P < 0.001), with a significantly (P < 0.001) greater reduction in both ALP and DPD/creatinine ratio. Of subjects crossed over from pamidronate to alendronate, 10/14 (71%) achieved remission, including 9/11 (82%) previously treated patients. We conclude that, in patients with previously untreated Paget's disease of bone, alendronate and pamidronate have similar efficacy in achieving biochemical remission. In patients previously treated with pamidronate, alendronate is more effective.

Stable or increasing bone mineral density in HIV-infected patients treated with nelfinavir or indinavir

BACKGROUND AND OBJECTIVES

To determine the factors contributing to changes in bone mineral density (BMD) over time in HIV-infected patients receiving highly active antiretroviral therapy (HAART).

METHODS

Analyses of lumbar spine BMD in 183 male Caucasian participants in the Western Australian HIV Cohort study, comprising a longitudinal analysis of data from 54 patients on stable HAART regimens, and a cross-sectional analysis comparing data from 131 protease inhibitor (PI)-treated patients and 52 PI-naive (including 28 antiretroviral treatment-naive) patients.

RESULTS

Average lumbar spine BMD remained stable or increased over the time frame considered. Although there was no evidence of a change of average BMD over time in patients receiving nelfinavir (P = 0.92), there was evidence of increasing bone density in the indinavir group (average increase, 0.31 z-score per year; P < 0.001). Lower initial z-scores in the longitudinal analysis were significantly associated with lower pre-HAART BMI (P = 0.003), consistent with results of the cross-sectional analysis in which lowest BMI prior to initial dual X-ray absorptiometry scan was associated with decreased BMD (P = 0.02, overall group). Although PI therapy was also associated with decreased BMD in a univariate analysis of the cross-sectional data (P = 0.04), this effect was abrogated in a multiple linear regression analysis (P = 0.11) with lowest BMI remaining significant (P = 0.04).

CONCLUSIONS

We found no evidence, overall, of accelerated bone loss in patients treated with nelfinavir- or indinavir-containing HAART regimens, and propose that indinavir therapy may be associated with an increase in bone mineral density over time. Pre-HAART BMI was an independent and powerful determinant of an individual's initial z-score in the longitudinal analysis, and adjustment for this effect in a cross-sectional analysis abrogated the association between PI therapy and decreased lumbar spine z-score.

Paget's disease: acquired resistance to one aminobisphosphonate with retained response to another

Twenty-five years after the first paper on etidronate in Paget's disease, there are few published papers that address bisphosphonate resistance as a specific clinical phenomenon. We report our data from two studies. Study 1 is a retrospective study of 20 patients with moderate to severe disease who were treated with intravenous (iv) pamidronate (221 +/- 18 mg [SEM]; range 60-360 mg), and after biochemical remission and relapse were retreated with generally larger iv dosage (293 +/- 28 mg; range 180-600 mg). The nadir bone turnover values were similar: plasma alkaline phosphatase (pAP) in 20 patients was 243 +/- 40 IU/l (mean +/- SEM) after the first course, and 267 +/- 44 IU/l after the second (reference range [RR] 35-135 IU/l). Likewise, fasting urinary hydroxyproline excretion (HypE) in 14 of the 20 patients was 4.5 +/- 1.1 micromol/LGF and 4.1 +/- 0.9 micromol/LGF, respectively (RR 0.40-1.92 micromol/LGF). However the minimum duration of biochemical remission was significantly shorter after the second course-10.9 +/- 1.7 months (first) and 5.6 +/- 0.9 months (second) (p < 0.03; Friedman's ANOVA n = 17). A subgroup of 10 patients who were followed for three courses showed a significantly higher pAP nadir in the third course. Study 2 is a prospective study of 40 patients, 23 previously untreated (NILPREV) and 17 previously treated with iv pamidronate (PAMPREV) and in biochemical relapse, who were randomly allocated to either oral alendronate 40 mg daily in 3 month units, or iv pamidronate 60 mg every 3 months. Treatment was continued until pAP and fasting urinary deoxypyridinoline/creatinine (Dpy/Cr) ratios (RR 5-27 micromol/mol) were both in the reference range, or a clear plateau in each marker developed. At baseline, there were no significant differences in either marker between the two NILPREV groups and between the two PAMPREV groups. Using log-transformed data, in NILPREV the pAP reductions were significant and similar over the first 6 months. However, although each Dpy/Cr reduction was also significant, the difference in responses favored alendronate (p < 0.015). In PAMPREV both markers showed no significant response to pamidronate; comparison showed a significantly greater response to alendronate (pAP p < 0.02; Dpy/Cr p < 0.002). Using two-way ANOVA, the pAP responses to alendronate in NILPREV and PAMPREV were similar and those to pamidronate were different (p = 0.034). The percentage of patients with both markers in the RR at 6 months or earlier were identical in NILPREV patients: alendronate 87% and pamidronate 87%. However in PAMPREV they were different: alendronate 83% and pamidronate 0% (p = 0.003). These data indicate: 1) patients treated with the same aminobisphosphonates for two courses show similar nadir values of bone turnover markers but a shorter remission time after the second course. In a third course the nadirs are significantly higher; and 2) in the alendronate/pamidronate comparison, NILPREV and PAMPREV patients showed similar pAP responses to alendronate, but significantly different responses to pamidronate. Thus, patients showing acquired partial resistance to one aminobisphosphonate (usually after two or more previous courses) are still capable of remission after exposure to another compound of the same class.

Elimination and biochemical responses to intravenous alendronate in postmenopausal osteoporosis

Postmenopausal women with established vertebral osteoporosis were studied for 2 years to determine the terminal elimination half-life and the duration of response to treatment with intravenous alendronate (30 mg) given over 4 days. The urinary excretion of alendronate followed a multiexponential decline. Approximately 50% of the total dose was excreted over the first 5 days, and a further 17% was excreted in the succeeding 6 months. Thereafter, there was a much slower elimination phase with an estimated mean terminal half-life of greater than 10 years (n = 11). Urinary excretion of hydroxyproline and calcium decreased significantly from pretreatment values by day 3, reaching a nadir by 1 week (40% and 67% decrease, respectively). Thereafter, hydroxyproline remained suppressed for the following 2 years. In contrast, urinary calcium excretion returned gradually toward pretreatment values over the first year and during the second year was comparable to pretreatment values. Serum activity of alkaline phosphatase activity decreased over 3 months (23% reduction), increased gradually thereafter, and returned to pretreatment values at month 24. Bone mineral density measured at the spine increased by approximately 5% during the first year and remained significantly higher than pretreatment values at 2 years. We conclude that a short course of high doses of intravenous alendronate is associated with a prolonged skeletal retention of the agent. This open study also suggests that this regimen has a sustained effect on bone turnover persisting for at least 1 year.

Alendronate in the treatment of Paget's disease of bone

We studied four treatment regimens of oral alendronate in 60 patients with active Paget's disease. Two groups received an oral daily dose of either 40 or 80 mg of alendronate for 3 months, followed by placebo for a further 3 months: the other two groups received treatment with 40 or 80 mg per day for 6 months. Activity of alkaline phosphatase and urinary hydroxyproline excretion were measured before, during, and after treatment, at intervals for a total follow-up of 1 year. A transiliac bone biopsy was performed in 24 patients before and after the treatment. An additional 16 patients had a third biopsy more than a year after stopping treatment. Alendronate induced a marked suppression in the urinary excretion of hydroxyproline within 2 weeks (p < 0.01) followed by a fall in serum activity of alkaline phosphatase at 1 month (p < 0.01) in all treatment groups. Nine months after the start of treatment patients treated with 80 mg for 6 months had a significantly lower mean alkaline phosphatase activity compared to the other treatment groups (p < 0.02), which persisted at 1 year (p < 0.05). Alkaline phosphatase decreased to within the laboratory reference range in all patients given 80 mg for 6 months. In contrast, alkaline phosphatase decreased to within the laboratory reference range in 73-83% of patients given 80 mg for 3 months and the 40 mg dose. Histomorphometric assessment showed a decrease in indices of bone turnover in the pagetic biopsies. None of the biopsies taken after treatment showed evidence of impaired mineralization of bone. Gastrointestinal side effects occurred in 25% of patients of whom two withdrew from treatment. We conclude that oral alendronate is an effective agent for the treatment of Paget's disease of bone.

The effects of intravenous alendronate in Paget's disease of bone

We studied the effects of intravenous alendronate on disease activity in 36 patients with active Paget's disease of bone. Alendronate was administered to 3 groups of 12 patients at doses of 2.5, 5, and 10 mg intravenously daily for 5 consecutive days. The patients were matched for disease activity. Symptomatic improvement was seen in at least 10 patients in each treatment group. Alendronate induced a dose-dependent suppression of biochemical indices of bone turnover in all patients. A significant reduction in the mean fasting urinary excretion of hydroxyproline occurred within 2 days of starting treatment, reaching a nadir at 2-4 weeks, which was most marked in patients receiving 10 mg of alendronate (p < 0.05). There was a slower fall in serum alkaline phosphatase activity with maximal suppression occurring 3 months after the start of treatment. The degree of suppression was least for those receiving 2.5 mg of alendronate (p < 0.05) but no difference in response was observed for the other dosages. The duration of response was also dose-related. A significant fall in the serum calcium and urinary excretion of calcium occurred from the second day of treatment but returned to pretreatment values by 4 months. A transient fall in the mean lymphocyte count was observed, which was similar for each group. This was associated with a short-lived fever in 3 patients receiving 10 mg, in 4 patients receiving 5 mg, and in 2 patients receiving 2.5 mg.(ABSTRACT TRUNCATED AT 250 WORDS)

The assessment of vertebral deformity: a method for use in population studies and clinical trials

The absence of specific criteria for the definition of vertebral fracture has major implications for assessing the apparent prevalence and incidence of vertebral deformity. Also, little is known of the effect of using different criteria for new vertebral fractures in clinical studies. We therefore developed radiological criteria for vertebral fracture in women for assessing both the prevalence and the incidence of vertebral osteoporosis in population and in prospective studies and compared these with several other published methods. Normal ranges for vertebral shape were obtained from radiographs in 100 women aged 45-50 years. These included ranges for the ratios of anterior/posterior, central/posterior and posterior/predicted posterior vertebral heights from T4 to L5. The predicted posterior height was calculated from adjacent vertebrae. In contrast to other methods, our definition of fracture required the fulfillment of two criteria at each vertebral site, and was associated with a lower apparent prevalence of fracture in the control women due to a lower false positive rate. The prevalence and incidence of vertebral deformity using different criteria were then compared in a series of women with skeletal metastases from breast cancer in whom radiographs were obtained 6 months apart. The prevalence of vertebral deformity and the specificity for deformity varied markedly with differing criteria. Using a cut-off of 3 standard deviations the prevalence of vertebral deformity in the women with breast cancer was 46%. Using other methods, the prevalences of deformity ranged from 33% to 74%. Over a 6-month interval 25% of patients with breast cancer sustained 61 deformities using our method, of which only 8% resulted from errors in reproducibility. The number of patients sustaining new deformities was increased twofold when assessed by other methods (45%-53%), but errors of reproducibility may have accounted for 21% of the new deformities. The magnitude and distribution of these errors have important implications for the apparent therapeutic efficacy of agents in clinical trials of osteoporosis. The rapid semi-automated technique for assessing vertebral deformities on lateral spine radiographs that we have developed has a high specificity, and reduces the impact of errors of reproducibility on estimates of prevalence and incidence. The method should prove a value in assessing vertebral deformity both in population studies and in prospective clinical trials.

Effective treatment of malignant hypercalcaemia with a single intravenous infusion of clodronate

Thirty patients with hypercalcaemia due to malignancy that persisted following rehydration, were treated with a single dose of the bisphosphonate, clodronate. Clodronate (1.5 g) was administered intravenously in 500 ml normal saline over 4 h. Serum and urine biochemistry were measured before and after treatment and the results were compared with data from 15 patients given the recommended regimen 300 mg intravenous clodronate daily for 5 consecutive days. The single infusion induced a rapid and significant fall in serum calcium, apparent at day 3 (P < 0.0001) that persisted to the end of follow-up at day 10 (P < 0.001). Eighty per cent (24/30) of patients became normocalcaemic. The response was associated with a significant decrease in fasting urinary calcium excretion, and no change in renal function, as judged by serum creatinine. The same dose of clodronate, given as 5 daily infusions, induced a comparable decrease in serum calcium, but was less rapid in onset so that at day 3 the serum calcium was significantly lower with the single infusion (P = 0.02). The calcium lowering effect of both regimens depended on the tumour type. We conclude that the single infusion of 1500 mg clodronate is as effective in reducing serum calcium as the same dose given over 5 days. The single infusion has a more rapid onset of effect, is more convenient than multiple infusions, and has no adverse effect on renal function.