Javaria M Khalid

University College London, London, ENG, United Kingdom

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Publications (7)17.96 Total impact

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    ABSTRACT: Background and Objectives Several countries have included medium-chain acyl-CoA dehydrogenase deficiency (MCADD) in their newborn screening programs. However, the sensitivity of the programs cannot be estimated directly as only individuals with a positive result undergo a definitive diagnostic test. We propose a framework to overcome this limitation and estimate the prevalence of disease, sensitivity of screening, and its yield relative to no screening. Study Design and Setting A Bayesian model simultaneously combined available prevalence data on the most common mutation of MCADD (c.985A>G) in screened and nonscreened populations using the relationship between true and apparent prevalence of disease. Data originated from screening pilots in England, disease surveillance studies, and published literature. Model validity and consistency were formally checked. Results True prevalence of c.985A>G homozygotes in England was 6.2 per 100,000 individuals, and the sensitivity of the screening program was 94% (95% confidence interval [CI]: 74, 100%) compared with a detection rate in nonscreened areas of 48% (95% CI: 30, 68%) by age of 5 years. Hence, the screening program detected 47% (95% CI: 30, 60%) additional cases compared with no screening. Conclusion The sensitivity of the screening program in England was high and our estimation approach could be adapted to inform other jurisdictions, rare diseases, and newborn screening programs.
    Journal of Clinical Epidemiology. 01/2014;
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    ABSTRACT: To describe the clinical presentation and sequelae, including salt-wasting crises of newly-diagnosed congenital adrenal hyperplasia (CAH) in children aged over 1 year in a contemporary population without screening. To appraise the potential benefit of newborn screening for late-presenting CAH. Active national surveillance undertaken in Great Britain prospectively from 2007-2009 through the British Paediatric Surveillance Unit. England, Wales and Scotland. Children first presenting aged 1-15 years with clinical features of CAH and elevated 17-hydroxyprogesterone. Fifty-eight children (26 [45%] boys) aged 1-15 years were reported; 50 (86%) had 21-hydroxylase deficiency. Diagnosis was precipitated by secondary sexual characteristics (n=38 [66%]; median age 5.8 [IQR] 4.8, 7.6) years, genital virilisation (8 girls; 3.2 [IQR 1.3, 7.3] years) or an affected sibling (n=8; 10.0 [IQR 7.4, 13.3] years). At least 33 (57%) children had advanced bone age and 13 (30%) were obese (body mass index ≥95th centile). No child had experienced a salt-wasting crisis. In Great Britain, 30 children aged 1-15 years present annually for the first time with CAH. Older children frequently manifest prematurely advanced epiphyseal and pubertal maturation and genital virilisation, which are often irreversible and likely to have long-lasting consequences for adult health and wellbeing. Almost one-third of affected children are obese before commencing steroid therapy. Newborn screening offers the potential to avoid serious clinical manifestations in older children with unrecognised CAH; however, it may also detect some children who would otherwise remain asymptomatic and for whom the benefit from treatment is uncertain.
    Archives of Disease in Childhood 09/2013; · 3.05 Impact Factor
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    ABSTRACT: To estimate the incidence of clinically diagnosed congenital adrenal hyperplasia (CAH), clinical features and age at first presentation. To assess the potential benefit of newborn screening for CAH. Active surveillance through the British Paediatric Surveillance Unit of all children aged under 16 years with newly diagnosed CAH, undertaken prospectively between August 2007 and August 2009. Twelve laboratories testing for CAH reported new diagnoses between August 2007 and January 2009. Reporting clinicians completed clinical questionnaires. England, Wales and Scotland. 144 children with CAH were reported, of whom 132 (92%) had 21-hydroxylase deficiency. Thirty-six (25%) children were Asian and 62 (43%; 95% CI 35% to 51%) were boys. Incidence of new diagnoses in children ≤ 16 years was 0.60 (95% CI 0.50 to 0.71) per 100,000. Eighty-six (59%; 36 boys) children were diagnosed in the first year of life (estimated birth prevalence 5.48 (95% CI 4.42 to 6.81) per 100,000), most (77; 89%) of whom presented in the first month of life. Virilised genitalia were found in three-quarters of girls. Twenty-seven newborns first presented with salt-wasting crises, of whom 18 (67%; 16 boys) presented on or after 14 days of age. Approximately one child in every 18 000 born in Great Britain has CAH. Similar numbers of boys and girls present clinically in the first year of life, but boys present with more severe manifestations, such as salt-wasting crises. Around 70% of newborns who first present with salt-wasting crisis would be detected earlier through newborn screening.
    Archives of Disease in Childhood 02/2012; 97(2):101-6. · 3.05 Impact Factor
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    ABSTRACT: Medium chain acyl-CoA dehydrogenase deficiency (MCADD) is a rare, life-threatening condition. Early diagnosis by screening asymptomatic newborns may improve outcome, but the benefit to newborns identified with variants not encountered clinically is uncertain. To estimate, overall and by ethnic group: screen-positive prevalence and predictive value (PPV); MCADD prevalence; proportion MCADD variants detected of predicted definite or uncertain clinical importance. All births in areas of high ethnic minority prevalence in England. Prospective multicentre pilot screening service; testing at age five to eight days; standardized screening, diagnostic and management protocols; independent expert review of screen-positive cases to assign MCADD diagnosis and predicted clinical importance (definite or uncertain). Approximately 1.5 million babies (79% white; 10% Asian) were screened. MCADD was confirmed in 147 of 190 babies with a positive screening result (screen-positive prevalence: 1.20 per 10,000; MCADD prevalence: 0.94 per 10,000; PPV 77% [95% CI 71-83]), comprising 103 (70%) with MCADD variants of definite clinical importance (95 white [95%]; 2 Asian [2%]) and 44 (30%) with variants of uncertain clinical importance (29 white [67%]; 12 Asian [28%]). One baby in every 10,000 born in England is diagnosed with MCADD by newborn screening; around 60 babies each year. While the majority of MCADD variants detected are predicted to be of definite clinical importance, this varies according to ethnic group, with variants of uncertain importance most commonly found in Asian babies. These findings provide support for MCADD screening but highlight the need to take account of the ethnic diversity of the population tested at implementation.
    Journal of Medical Screening 12/2011; 18(4):173-81. · 2.35 Impact Factor
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    ABSTRACT: Background Congenital Adrenal Hyperplasia (CAH) is caused by recessively inherited enzyme deficiencies in cortisol production and affects an estimated one child in every 17 000 born in the UK. Children may present with life-threatening adrenal or salt wasting crisis, virilised female genitalia, accelerated growth or precocious puberty. However, detailed information on the short term clinical outcome of CAH is lacking.AimTo report the spectrum of short-term clinical outcomes at 1 year following diagnosis for children with CAH diagnosed before age 16 years in the UK.Methods Active surveillance through the British Paediatric Surveillance Unit for 25 months from August 2007 of newly diagnosed CAH in any child
    Archives of Disease in Childhood - ARCH DIS CHILD. 01/2011; 96(1).
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    ABSTRACT: Although octanoylcarnitine (C8) concentrations measured from newborn screening dried blood spots are used to identify those at high risk of medium-chain acyl-CoA dehydrogenase deficiency (MCADD), age-related reference values are currently not available for unaffected newborn populations. Because age at sampling may vary within and between screening programs, variations in C8 concentrations by age may affect screening program performance. We determined whether C8 concentrations vary by age at sampling, sex, birth weight, or gestational age in unaffected newborns. We analyzed C8 concentrations from 227,098 unaffected newborns, including 179,729 from 6 English laboratories participating in a multicenter study and 47,369 from the single laboratory serving the New South Wales (NSW) Newborn Screening Program in Australia. In England, the majority of samples were collected at age 5-8 days and analyzed underivatized by use of tandem mass spectrometry (MS/MS); in NSW, samples were obtained at a median age of 3 days and analyzed derivatized by MS/MS. Information on infants' sex, birth weight, gestation, hospitalization, and transfusion status was recorded at time of sampling. C8 concentrations did not vary significantly by age at sampling, sex, birth weight, or gestational age and remained relatively constant during the first 2 weeks of life in unaffected babies being screened for MCADD. Newborn MCADD screening programs using this biomarker for screening samples collected after the first day and during the first 14 days of life do not need to adjust cutoff values to account for postnatal age, prematurity, or size at birth.
    Clinical Chemistry 04/2010; 56(6):1015-21. · 7.15 Impact Factor
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    ABSTRACT: It has been suggested that homozygous c.985A>G medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is a disease of White ethnic origin but little is known regarding its ethnic distribution. We estimated ethnic-specific homozygous c.985A>G MCADD birth prevalence from a large-scale UK newborn screening study. Homozygous c.985A>G MCADD cases were ascertained in six English newborn screening centres between 1 March 2004 and 28 February 2007 by screening approximately 1.1 million newborns using tandem mass spectrometry analysis of underivatised blood spot samples to quantitate octanoylcarnitine (C8). Follow-up biochemistry and mutation analyses for cases (mean triplicate C8 value >/=0.5 micromol/L) were reviewed to confirm diagnosis. Ethnicity was ascertained from clinician report and denominators from 2001 UK Census estimates of ethnic group of children less than one year. Sixty-four infants were c.985A>G MCADD homozygotes (overall prevalence 5.8 per 100,000 live births; 95% CI 4.4-7.2). Sixty (93%) were White, two (3%) were mixed/other and two were of unknown ethnic origin. No Asian or Black homozygotes were identified. Proportions of White, mixed/other, Asian and Black births in screening regions were estimated, yielding homozygous c.985A>G MCADD birth prevalence of 6.9 per 100,000 (95% CI 5.2-8.8) in White, and 95% CI estimates of 0-2.7 per 100,000 in Asian and 0-5.8 in Black populations. The c.985A>G carrier frequency in the White group was estimated at one in 65 (95% CI 1/74, 1/61) under Hardy-Weinberg conditions. c.985A>G homozygous MCADD is not found in Black and Asian ethnic groups that have been screened at birth in England. This is consistent with the earlier published observations suggesting that MCADD due to the c.985A>G mutation is a disease of White ethnic origin.
    Journal of Medical Screening 01/2008; 15(3):112-7. · 2.35 Impact Factor