Prevalence of permanent childhood hearing impairment in the United Kingdom and implications for universal neonatal hearing screening: questionnaire based ascertainment study.

OBJECTIVE: To estimate the prevalence of confirmed permanent childhood hearing impairment and its profile across age and degree of impairment in the United Kingdom. DESIGN: Retrospective total ascertainment through sources in the health and education sectors by postal questionnaire. SETTING: Hospital based otology and audiology departments, community health clinics, education services for hearing impaired children. PARTICIPANTS: Children born from 1980 to 1995, resident in United Kingdom in 1998, with severe permanent childhood hearing impairment (hearing level in the better ear >40 dB averaged over 0.5, 1, 2, and 4 kHz). MAIN OUTCOME MEASURES: Numbers of cases with date of birth and severity of impairment converted to prevalences for each annual birth cohort (cases/1000 live births) and adjusted for under ascertainment. RESULTS: 26 000 notifications ascertained 17 160 individual children. Prevalence rose from 0.91 (95% confidence interval 0.85 to 0.98) for 3 year olds to 1.65 (1.62 to 1.68) for children aged 9-16 years. Adjustment for under ascertainment increased estimates to 1.07 (1.03 to 1.12) and 2.05 (2.02 to 2.08). Comparison with previous studies showed that prevalence increases with age, rather than declining with year of birth. CONCLUSIONS: Prevalence of confirmed permanent childhood hearing impairment increases until the age of 9 years to a level higher than previously estimated. Relative to current yields of universal neonatal hearing screening in the United Kingdom, which are close to 1/1000 live births, 50-90% more children are diagnosed with permanent childhood hearing impairment by the age of 9 years. Paediatric audiology services must have the capacity to achieve early identification and confirmation of these additional cases.

The spectrum of postmortem ocular findings in victims of shaken baby syndrome.

BACKGROUND: Ophthalmologists and ocular pathologists are called on to help identify children who have undergone violent shaking. The objective of this study was to describe the spectrum of postmortem ocular findings in victims of shaken baby syndrome and to correlate the ocular findings with the nonocular features found at autopsy. METHODS: The ocular pathology registry at the University of Ottawa Eye Institute was reviewed to identify all victims of fatal shaken baby syndrome whose eyes had been submitted for examination between Apr. 1, 1971, and Dec. 31, 1995. Autopsy reports were accessed from the hospital charts of the identified patients. RESULTS: Six patients, aged 1 to 34 months, were identified. Intraocular findings ranged from a focal globular hemorrhage at the posterior pole to extensive intraocular hemorrhage involving the entire retina with perimacular folds. All the children had evidence of optic nerve sheath hemorrhage. Nonocular findings included intracranial hemorrhage (in all cases), skull fracture (in two), rib fractures (in three) and high spinal cord hemorrhage (in four). The extent of the intraocular hemorrhage was not consistent with the nonocular findings. INTERPRETATION: Abused children may display a range of postmortem ocular findings, with intraocular hemorrhage varying from minimal to severe. These findings may not correlate with the severity of the child's other injuries. The presence of any retinal or optic nerve sheath hemorrhage in an infant, in the absence of an appropriate explanation for these findings, should raise suspicion of child abuse.

Non-use of cochlear implants by post-lingually deafened adults.

OBJECTIVES: To document the occurrence of medical/surgical complications in the provision of cochlear implants to a cohort of post-lingually deafened adult patients; to compare cumulative mortality in the cohort with cumulative mortality predicted from an aged-matched control population; to relate the occurrence of medical/surgical complications to the patient's position in the case series; to identify risk factors for elective non-use of implants; and to examine the impact of complications, mortality and elective non-use on the cost of creating a successful user of a cochlear implant. DESIGN: Longitudinal prospective observational study. SETTING: Nine hospitals in the UK, which received central funding between 1990 and 1994 to participate in a programme of adult implantation. PARTICIPANTS: All 313 post-lingually deafened adults who received multichannel cochlear implants in this programme. MAIN OUTCOME MEASURES: Status of patients in July 1998 (dead, an elective non-user or a user); duration of use prior to death or elective non-use; costs of creating and sustaining a successful user; ability to identify environmental sounds; self-reported benefit. RESULTS: Cumulative mortality after 7.5 years was 6.3% (95% CI 2.5-10.1%) and was no different from cumulative mortality predicted from life expectancy in the general population. Cumulative elective non-use was stable at 6.3% (95% CI 3.6%-9.1%) between 4 and 7 years after implantation but rose to 11.0% (95% CI 1.7%-20.3%) at 7.5 years after implantation. Major medical/surgical complications were experienced by 25/313 patients (8.0%). The occurrence of such complications declined to ca. 1% over the first 50 cases in a hospital's case series. For patients who were users, self-reported benefit did not differ between patients who had experienced complications and those who had not. Older age at implantation, greater duration of deafness prior to implantation or an early position in a hospital's case series were not significant risk factors for elective non-use. Experiencing a major complication was a marginally significant risk factor (odds ratio = 3.2, 95% CI 1.0-10.6). Low auditory performance (odds ratio = 8.2, 95% CI 2.1-31.9) and low self-reported benefit (odds ratio = 19.6, 95% CI 4.6-84.4) were significant risk factors. Medical/surgical complications raised the cost of creating a successful user by less than 1%. Elective non-use raised the cost by between 5% and 10%. CONCLUSIONS: Medical/surgical complications were generally managed successfully without detriment to benefit; life expectancy in the general population can be used to predict the length of time for which patients have the potential to use cochlear implants; patients who experience little benefit are most at risk for elective non-use; given the high cost of cochlear implantation, benefit should be monitored to allow early rehabilitative intervention in cases of low benefit; patient cohorts such as the present one should continue to be followed up with a view to identifying pre-operative risk factors for elective non-use.

Paediatric cochlear implantation and health-technology assessment.

Cochlear implants are provided to children on the basis of the hypothesis that short-term outcomes in auditory receptive skills will translate via a cascade of medium-term outcomes into greater social independence and quality of life. The medium-term outcomes include: (i) enhanced engagement and integration in primary education, leading to greater scholastic achievement; (ii) enhanced social versatility and robustness, permitting a successful transition to secondary education; and (iii) enhanced educational qualifications, allowing greater opportunities in further education and employment. A sufficient number of children have used implants for long enough for it to be feasible to establish whether the first two medium-term outcomes are being achieved and, if so, at what cost in the provision of health care and education. The first part of this paper discusses alternative research designs that could address these issues. Although a prospective randomised controlled trial would provide the most powerful evidence for or against the hypothesis, it is implausible that adequate compliance with randomisation to treatments could be sustained to give such a study sufficient power. The most powerful realisable design would be a large-scale cross-sectional comparison of implanted children and matched groups of their non-implanted peers. The second part of the paper describes the results of a speculative cost-benefit analysis that seeks to identify the cost to society of providing implants to children. The analysis is based on measured costs of health care, but on estimates of costs and cost-savings in other domains. It indicates that paediatric implantation could be cost-neutral in the UK, provided that implantation saved pound sterling 3000/year in the cost of education, pound sterling 1000/year in other domains, and permitted an increase in personal income of 25% of the national median household income. These savings might be realised if implantation permitted sufficient facility in spoken language to allow every implanted child to enter mainstream education.

Dichotic pitches as illusions of binaural unmasking. I. Huggins' pitch and the "binaural edge pitch".

The two most salient dichotic pitches, the Huggins pitch (HP) and the binaural edge pitch (BEP), are produced by applying interaural phase transitions of 360 and 180 degrees, respectively, to a broadband noise. This paper examines accounts of these pitches, concentrating on a "central activity pattern" (CAP) model and a "modified equalization-cancellation" (mE-C) model. The CAP model proposes that a dichotic pitch is heard at frequency f when an individual across-frequency scan in an interaural cross-correlation matrix contains a sharp peak at f. The mE-C model proposes that a dichotic pitch is heard when a plot of interaural decorrelation against frequency contains a peak at f. The predictions of the models diverge for the BEP at very narrow transition bandwidths: the mE-C model predicts that salience is sustained, while the CAP model predicts that salience declines and that the dominant percept is of the in-phase segment of the noise. Experiment 1 showed that the salience of the BEP was sustained at the narrowest bandwidths that could be generated (0.5% of the transition frequency). Experiment 2 confirmed that the pitch of a BEP produced by a 0.5% transition bandwidth was close to the frequency of the transition band. Experiment 3 showed that pairs of simultaneous narrow 180-degree transitions, whose frequencies corresponded to vowel formants, were perceived as the intended vowels. Moreover, the same vowels were perceived whether the in-phase portion of the noise lay between the two transition frequencies or on either side of them. In contrast, different patterns of identification responses were made to diotic band-pass and band-stop noises whose cutoff frequencies corresponded to the same formants. Thus, the vowel-identification responses made to the dichotic stimuli were not based on hearing the in-phase portions of the noise as formants. These results are not predicted by the CAP model but are consistent with the mE-C model. It is argued that the mE-C model provides a more coherent and parsimonious account of many aspects of the HP and the BEP than do alternative models.

Dichotic pitches as illusions of binaural unmasking. II. The Fourcin pitch and the dichotic repetition pitch.

The predictions of three models are compared with respect to existing experimental data on the perception of the Fourcin pitch (FP) and the dichotic repetition pitch (DRP). Each model generates a central spectrum (CS), which is examined for peaks at frequencies consistent with the perceived pitches. A modified equalization-cancellation (mE-C) model of binaural unmasking [Culling and Summerfield, J. Acoust. Soc. Am. 98, 785-797 (1995)] generates a CS which reflects the degree of interaural decorrelation present in each frequency channel. This model accounts for the perceived frequencies of FPs, but produces no output for DRP stimuli. A restricted equalization-cancellation (rE-C) model [Bilsen and Goldstein, J. Acoust. Soc. Am. 55, 292-296 (1974)] sums the time-varying excitation in corresponding frequency channels, without equalization, to form a CS. A central activity pattern (CAP) model [Raatgever and Bilsen, J. Acoust. Soc. Am. 80, 429-441 (1986)] generates a CS by scanning an interaural cross-correlation matrix across frequency. The rE-C and CAP models yield inaccurate predictions of the perceived frequencies of FPs, but predict the occurrence of the DRP and its correct pitch. The complementary predictions of the mE-C model compared to the rE-C and CAP models, together with the evidence that the FP is clearly audible for the majority of listeners, while the DRP is faintly heard by a minority of listeners, suggest that the mE-C model provides the best available account of the FP, and that the DRP is produced by a separate mechanism.

Necrotizing fasciitis caused by group A streptococcus infection after laser blepharoplasty.

PURPOSE: To describe a patient who developed early signs of necrotizing fasciitis after undergoing laser blepharoplasty. METHODS: A 36-year-old woman developed wound discharge, wound dehiscence, and facial swelling 66 hours postblepharoplasty. Cloxacillin was administered but changed to high-dose intravenous penicillin G and clindamycin when the eyelid cultures grew group A streptococcus (an organism capable of causing necrotizing fasciitis organism). RESULTS: The patient was treated with intravenous antibiotics for 10 days followed by 3 weeks of oral medications. The wounds healed spontaneously with an excellent result. CONCLUSIONS: Infection postblepharoplasty is rare. When it occurs, tissue destruction can be potentially devastating. Prompt diagnosis, intravenous antibiotics, and close follow-up are essential.

Cost-effectiveness considerations in pediatric cochlear implantation.

OBJECTIVE: To summarizes the results of cost-utility analyses of pediatric cochlear implantation (CI) in the United Kingdom. METHOD: Analysis is based on the direct costs of medical and rehabilitative management and also on emerging evidence that implantation leads to a shift in educational placements in favor of mainstreaming with support. RESULT: The resulting cost-utility ratio falls on the margin of the range considered acceptable within the British health-care system. The analysis also suggests that pediatric CI could be acceptably cost-effective. CONCLUSION: The next step should be to measure the costs of alternative educational settings directly.

Periocular necrotizing fasciitis: a review of five cases.

OBJECTIVE: The purpose of the study is to display a spectrum of clinical presentations of periocular necrotizing fasciitis caused by group A streptococci and to discuss recent trends and treatment of this disease. DESIGN AND INTERVENTION: A case series of five patients (four female and one male) was seen between July 1990 and January 1995 in four university centers. All had clinical evidence of periocular necrotizing fasciitis and grew group A streptococci on wound cultures or had serologic evidence of streptococcal infection. Details of patient presentation, treatment, and outcome are examined. RESULTS: The five patients showed a spectrum of clinical severity from a necrotizing infection confined to the eyelid to a potentially fatal, severe shock-like syndrome characterized by sepsis and multiorgan system failure. A history of trauma often was absent. Patients were treated successfully by a combination of appropriate antibiotics and surgical debridement. CONCLUSIONS: Group A streptococci can cause severe necrotizing infections of the eyelids. Early recognition and prompt treatment can be essential to these patients' survival.

Post-traumatic corneal mucormycosis caused by Absidia corymbifera.

OBJECTIVE: The purpose of the study was to report a case of mycotic keratitis caused by the organism Absidia corymbifera (class Zygomycetes, order Mucorales, family Mucoraceae). DESIGN: Case report. PARTICIPANT: A healthy 37-year-old farmer scratched his left cornea on a galvanized nail while working in his barn. Within 24 hours, an infiltrate in the interior cornea developed that advanced superiorly, reducing the vision to hand motion by the following day. He was treated with topical and systemic antibiotics and antifungal medications, but the infiltrate spread to the adjacent nasal limbus. INTERVENTION: An 11-mm penetrating keratoplasty was performed with an adjacent nasal 7-mm superficial lamellar sclerectomy. MAIN OUTCOME MEASURES: Pathologic examination of the keratoplasty specimen. RESULTS: Corneal cultures grew A. corymbifera. The organisms were identified in tissue sections by light, fluorescent, electron, and immunoelectron microscopy. CONCLUSIONS: The authors believe that this is the first reported case of keratitis caused by an Absidia species and, as such, represents an unusual form of mucormycosis in an otherwise healthy individual.

Self-rated hearing disability in candidates for cochlear implants.

A previous scheme for quantification of hearing disability based on self-rating required extrapolation towards the upper end of the range due to lack of data from severely and profoundly impaired subjects. Suitable data have become available more recently from the UK programme evaluating cochlear implantation, thereby providing self-ratings by 465 people with 1-2-3-kHz average hearing threshold levels of 95 dB or greater. The ratings obtained fit the previous extrapolation extremely well. The scheme, therefore, can be applied with confidence to people throughout the range of hearing impairment.

Responses of ventral cochlear nucleus onset and chopper units as a function of signal bandwidth.

1. The responses of units in the ventral cochlear nucleus in anesthetized guinea pigs have been measured to best-frequency tones, noise bands geometrically centered around the unit best frequency, and noise bands asymmetrically positioned around the best frequency. 2. Each unit isolated was characterized using peristimulus time histograms (PSTHs) to best-frequency tones at 20 and 50 dB suprathreshold, frequency-intensity response areas and rate-versus-level functions in response to best-frequency tones and wideband noise. The data reported here are derived from full analyses of 5 chopper units and 17 onset units. The onsets were divided into onset-I (OnI), onset-L (OnL), and onset-C (OnC) by the criteria described by Winter and Palmer: the PSTHs of OnI units show only an onset response, OnL units respond with a single spike at onset followed by a low level of sustained activity, and OnC units have PSTHs with one to four onset peaks and low levels of sustained discharge. 3. In response to geometrically centered noise bands of constant spectral density, the discharge of chopper units and one OnI unit increased over a relatively narrow range of bandwidths, corresponding to the equivalent rectangular bandwidth calculated from their response area, and then became constant. In contrast, OnL and OnC units showed increases in discharge rate with noise bandwidth over very wide ranges of bandwidth. The growth of the discharge rate with noise bandwidth was approximately linear on double logarithmic axes and therefore could be described by a power function with an exponent of 0.37. This relation held even for noise levels near threshold. 4. When noise bands with constant spectral density (at the input to the earphone) were presented with one edge fixed at the unit's best frequency, the discharge rate of most chopper units and the one OnI unit increased over a narrow range of bandwidths and then became constant. This pattern was observed irrespective of whether the second edge of the noise was progressively increased above, or decreased below, the best frequency. For two of the chopper units, in which lateral inhibitory sidebands could be demonstrated, increasing the noise bandwidth led first to increases and then to decreases in the discharge rate as the noise energy impinged upon the sideband. The chopper units act like energy detectors with a filter corresponding to their single tone response area, but, for some units, with the addition of inhibitory sidebands. 5. For the OnL and OnC units, increasing the noise bandwidth above or below best frequency caused progressive increases in the discharge rate over wide ranges of bandwidth. These increases occurred even for low noise spectral densities. The growth in discharge rate for these onset units was well fitted at all spectral density levels by power functions: one above best frequency and one below. At levels of the noise 40 dB above the unit threshold, the point at which the discharge rate reached 90% of its maximum was, on average, about 2 octaves below best frequency and 1 octave above. For some onset units, changes in the discharge rate were seen as the noise bandwidth was varied over about 14 kHz, which is about one-third of the total frequency hearing range of the guinea pig. 6. The data for onset units is consistent with the hypothesis that onset units in the ventral cochlear nucleus achieve their precision in the temporal domain by integration of the inputs from auditory nerve fibers with a wide range of best frequencies. The range of frequency over which onset units integrate frequency matches that of the inhibitory input to dorsal cochlear nucleus neurons, suggesting a possible role as an inhibitory interneuron.

Toxicity of intravitreal interferon alpha-2b in the rabbit.

OBJECTIVE: To investigate the toxicity of single doses of intravitreally administered interferon alpha-2b in the New Zealand white albino rabbit. INTERVENTIONS: One eye each of six rabbits received an intravitreal injection of 1000, 10,000, 100,000, 500,000, 1 million or 2 million units of interferon alpha-2b reconstituted in 0.1 mL of balanced salt solution. The fellow eye of the first three rabbits received an intravitreal injection of the same volume of balanced salt solution. OUTCOME MEASURES: Media opacities, toxic effects to the retina, optic nerve or other ocular structures. RESULTS: The injection of 2 million units of interferon alpha-2b elicited an immediate dense vitreous haze that largely cleared within 24 hours as well as numerous intraretinal hemorrhages that were no longer visible 7 days after injection. Histopathological study of this eye 14 days after injection showed a diffuse mixed inflammatory cell infiltrate with retinal vacuolation and ganglion cell dropout. In the remaining eyes, to dosages of 1 million units, the agent produced no clinically or pathologically evident toxic ocular effects. CONCLUSIONS: Interferon alpha-2b appears to be safe and well tolerated up to dosages of 1 million units.

Categories of Auditory Performance.

Categories of Auditory Performance (CAP) is an index consisting of eight performance categories arranged in order of increasing difficulty. It has been used to categorize 53 children who had been deafened below the age of 3. The children were assessed by means of the CAP before implantation, and over the following 3 years. Before implantation, only 2 of the children showed awareness of environmental sounds; immediately after initial tuning, all children showed awareness of environmental sounds, and 50% showed awareness of speech sounds. Their auditory receptive abilities gradually developed over the 3-year period, and by the 3-year assessment interval, 80% were understanding phrases without lipreading, and 40% were understanding conversation. Using these data, we predict that 90% of such children will understand conversation without lipreading 5 years after initial tuning.

Air guns: the main cause of enucleation secondary to trauma in children and young adults in the greater Ottawa area in 1974-93.

OBJECTIVES: To determine the proportion of enucleation procedures attributable to injuries from air guns in people aged 18 years or less and to identify the associated pathological findings. DESIGN: Case series. SETTING: Ophthalmic Pathology Registry, University of Ottawa, and affiliated Children's Hospital of Eastern Ontario (Ottawa), Ottawa General Hospital and Ottawa Civic Hospital. In addition, information on air gun injuries from April 1990 to December 1993 was obtained from the Canadian Hospitals Injury Reporting and Prevention Program (CHIRPP) database, with data from 10 pediatric and 5 general hospitals across Canada. PATIENTS: All patients aged 18 years or less who underwent enucleation between Jan. 1, 1974, and Dec. 31, 1993. RESULTS: Eighty-five patients were identified as having undergone enucleation. Trauma accounted for 51 cases (60%), of which 13 (25%) were caused by air guns, the largest single cause of enucleation secondary to trauma. Overall, air gun injuries accounted for 15% of enucleation procedures, whereas retinoblastoma accounted for 21%. All air gun injuries were in boys (median age 14 years, range 9 to 16 years). Of the 13 eyes with air gun injuries 7 had ocular perforation and 6 had ocular penetration. In all cases the intraocular structures were severely disrupted. The CHIRPP database included 165 air gun injuries; 32 were to the eye or ocular adnexa, resulting in 26 hospital admissions. CONCLUSIONS: Air guns were the largest single cause of enucleation secondary to trauma in our study. These guns are widely available in Canada and are unrestricted at muzzle velocities capable of causing death or serious injury, especially to the eye. We feel that air guns should be licensed only to people aged 16 to 18 years or older and that education in their use should be mandatory.

Clinical evaluation and test-retest reliability of the IHR-McCormick Automated Toy Discrimination Test.

The IHR-McCormick Automated Toy Discrimination Test (ATT) measures the minimum sound level at which a child can identify words presented in quiet in the sound field. This 'word-discrimination threshold' provides a direct measure of the ease with which a child can identify speech and a surrogate measure of auditory sensitivity. This paper describes steps taken to maximize the test-retest reliability of the ATT and to enable it to measure word-discrimination thresholds in noise as well as in quiet. It then describes the results of a clinical evaluation of the ATT in which paediatric audiologists measured word-discrimination thresholds in quiet from 215 successive attendees (in the age range 2 to 13 years) at a paediatric audiology clinic presenting over a 2-month period. When children with atypical cognition or delayed development of language were excluded, 72% of the children provided two word-discrimination thresholds and 83% provided at least one word-discrimination threshold. Children who failed to provide word-discrimination thresholds were generally younger than four years of age. Although a few children who could not perform pure-tone or warble-tone audiometry managed to provide word-discrimination thresholds, most children who could perform the ATT could also perform pure-tone audiometry. The average pure-tone threshold in the better-hearing ear could be predicted from the word-discrimination threshold with a 95% confidence interval of +/- 13 dB. The test-retest reliability of the ATT was measured in two ways. First, to enable comparison with published results, the within-subjects standard deviation of word-discrimination thresholds was calculated. It varied as a function of age and degree of impairment, but was never worse than 3.3 dB. Children of four years of age and older displayed the adult reliability of 2.3 dB. Second, the variability of absolute differences between word-discrimination thresholds was calculated. It was such that a change of 7 dB between two runs of the test (e.g. aided and unaided) would be expected to occur by change less than one time in 20. These results extend previous evaluations of the ATT to a clinically representative population and confirm that word-discrimination thresholds provide a useful complement to warble-tone and pure-tone audiometry.

Lip-reading the BKB sentence lists: corrections for list and practice effects.

Two groups of 21 adult subjects with normal hearing viewed the video recordings of the Bamford-Kowal-Bench standard sentence lists issued by the EPI Group in 1986. Each subject viewed all of the 21 lists and attempted to write down the words contained in each sentence. One group lip-read the lists with no sound (the LR:alone condition). The other group also heard a sequence of acoustic pulses which were synchronized to the moments when the talker's vocal folds closed (the LR&Lx condition). Performance was assessed both by loose (KW(L)) and by tight (KW(T)) keyword scoring methods. Both scoring methods produced the same pattern of results: performance was better in the LR&Lx condition; performance in both conditions improved linearly with the logarithm of the list presentation order number; subjects who produced higher overall scores also improved more with experience of the lists. The data were described well by a logistic regression model which provided a formula which can be used to compensate for practice effects and for differences in difficulty between lists. Two simpler, but less accurate, methods for compensating for variation in inter-list difficulty are also described. A figure is provided which can be used to assess the significance of the difference between a pair of scores obtained from a single subject in any pair of presentation conditions.

Bisphosphonate space measurement in Paget's disease of bone treated with APD.

The bisphosphonate space (BPS) is a quantitative measurement of skeletal uptake of 99mTc-HMDP. We measured BPS in 36 patients with Paget's disease of bone, both before and 6 months after treatment with intravenous APD (disodium pamidronate) infusions. BPS fell after treatment, but proportionally less than serum alkaline phosphatase (ALP) and fasting urinary hydroxyproline/creatinine (HYPRO). There was no dose-response relationship between the dose of APD given and the percentage reduction in ALP and HYPRO at 6 months. Log dose of APD/pretreatment BPS, however, predicted the percentage reduction in ALP and HYPRO very well, and from the respective regression equations it was possible to predict the dose of APD needed to achieve normal values of ALP and HYPRO. In the 10 patients who achieved a normal ALP and 9 patients a normal HYPRO after more than 6 months treatment with APD (range 7-18 months), the predicted dose of APD agreed closely with the actual dose. In conclusion, our data support the idea that log dose APD/pretreatment BPS is a valid predictor of biochemical response in Paget's disease.