Newborn screening: Need of the hour

INTRODUCTION

Newborn screening (NBS) is the process by which newborns are screened just after birth for disorders that can cause severe illness or death unless detected and treated early. The delay or lack of diagnosis of an Inborn Error of Metabolism or other conditions which can be detected at birth, for example, hypothyroidism, G6PD deficiency, etc., can lead to severe mental deterioration. NBS tests newborns for certain metabolic and other disorders so that intervention is possible before symptoms or mental and/or physical disabilities develop. It is a norm in the developed countries and is recommended to prevent morbidity and mortality. Depending on the incidence, different countries screen for disorders ranging between 5 and 50+ disorders.

NBS was introduced in early 1960s by the pioneering work of Dr. Robert Guthrie in the USA, with the discovery of bacterial inhibition assay to detect Phenylketonuria from dried blood spots.^[1] As the concept of NBS was accepted as an essential preventive public health policy, newer techniques developed and soon began to include other IEMs. Since its commencement NBS has progressed with increase in the number of metabolic/genetic disorders screened, type of samples used (from invasive to non-invasive), and improvements in technology (from bacterial inhibition assays to ELISA and RIA and now to LC/MS/MS techniques). In 1990, it was proposed that MS/ MS could be used to test for multiple analytes simultaneously in dried blood spots^[2] and about 40 conditions are now screened from a single blood spot by LC/MS/MS in routine NBS programs.^[3,4]

In India, NBS was first carried out by Dr. Appaji Rao and Dr. Radha Rama Devi. Subsequently, many small studies were carried out at various centers across India and now many private hospitals and labs have initiated their own NBS programs. Many state level NBS programs have been initiated and of note among these are the Chandigarh Program initiated in 2007 which screened for CH, CH, and G6PD;^[5] Kerala State NBS program^[6] and Goa state NBS Program carried out by Dr. Rohit Cariappa.^[7] However, NBS as a National Health Service program is yet to be initiated in India.

WORLD HEALTH ORGANIZATION (WHO) GUIDELINES

NBS is not simply a test for diagnosing disorders but a coordinated comprehensive system consisting of other aspects such as education, follow-up of abnormal results and confirmatory testing, diagnosis, treatment, management, periodic outcome evaluation, quality assurance, and evaluation of the whole program. The WHO has issued guidelines and criteria for selecting disorders in NBS program. Wilson and Jungner in 1996 have outlined the selection criteria for disorders in NBS program. These criteria are applicable to systematic or population-based screening of any type of disease and not only to inherited disorders.

Box 1: Wilson-Jungner criteria for disease selection in NBS

1. The condition should be an important health problem

2. Natural history of the condition should be well understood

3. It should be detectable at an early age

4. Treatment at an early stage should be beneficial

5. Suitable test should be devised for early detection

6. The test should be acceptable

7. Intervals for repeating the test should be available

8. Adequate health service provision should be made for the extra clinical workload resulting from the screening

9. The risks, both physical and psychological should be less than the benefits.

10. The cost should be balanced against the benefits.

Congenital hypothyroidism (CH) is the most common preventable cause of mental retardation. The world-wide incidence is 1:2500–2800 live births. Thyroid dysgenesis is the most common cause accounting for 75–80% of all cases of CH. In India, the exact incidence of this disorder is not known, but it seems to have a much higher incidence than the rest of the world.^[8-11] It not only constitutes the most common cause of preventable mental retardation but also the therapy is easily available and economically feasible to all. First NBS program for CH was started at BJ Wadia Hospital in Mumbai in 1982 using cord blood TSH and subsequently in 1984 using post-natal T4 on DBS.^[12]

Ideally universal NBS at 48–72 h of life should be done for detecting CH. If screening is being done only for CH, the cord blood may also be used. Three approaches are used for screening:^[13]

1. Primary TSH (backup T4): T4 is measured only if TSH is >20 mU/L

2. Primary T4 (backup TSH): TSH is measured if T4 is <6.5 ug/dL

3. Both T4 and TSH: Both measured simultaneously. More sensitive approach but is expensive.

Primary TSH screen is more sensitive and specific for diagnosis of primary CH. Abnormal value on screening (T4 <6.5 ug/dL and TSH >20 mU/L) should always be confirmed by a repeat sampling and assays done on liquid blood samples.^[14] Most centers initiate treatment after drawing the blood samples for confirmatory results and decision to withhold or continue treatment is taken after obtaining venous blood report.

G6PD deficiency is the most common enzyme deficiency affecting estimated 400 million people all over the world. It is also the most common genetic disorder in India. Although the exact incidence is not known, various studies have reported an incidence ranging from 2% to 27.9% in different communities.^[8,15] It is an X-linked recessive disorder presenting with hemolytic anemia and prolonged jaundice and causes significant morbidity and mortality in childhood. There are no primary interventions available for this disease and the only way to avoid adverse outcomes is to recognize it early in life and prevent exposure to agents which can trigger hemolysis. NBS helps to identify these individuals at an early age.

NBS for G6PD has been successfully implemented in countries such as the USA, Malaysia, Singapore, Taiwan, Hong Kong, Philippines, the Middle East, and Europe. In India, NBS for G6PD deficiency has long been perceived by public and pediatric health experts. Introduction of screening program will substantially decrease the hospital admissions due to acute hemolysis, thereby reducing the number of blood transfusions and dialysis needed.

Cystic fibrosis is the most lethal, autosomal recessive monogenic disorder caused due to an abnormal transport of chloride ions across the apical membrane of the epithelial cells. The sweat glands are relatively impermeable to chloride ions resulting in increased concentration of chloride in the sweat reaching the skin surface. To maintain electro neutrality, the reabsorption of sodium ions by the sweat glands is also reduced, thereby increasing the concentration of sodium in the sweat.^[16] The prevalence of this disorder in India is not known, however, there have been a few studies to study the prevalence and the common mutations in the CFTR gene in the Indian population.^[17-19] Although there is no intervention available for this disorder, early detection can help in reducing the cost of tedious diagnostic procedures later in life. Screening for this is done by analyzing the levels of IRT in DBS.

Congenital adrenal hyperplasia is a group of rare autosomal recessively inherited disorders of cortisol biosynthesis. The classic defect occurs in two forms as CAH with salt wasting and as simple virilizing CAH without salt wasting. The incidence of CAH varies worldwide according to ethnicity and geography. The exact incidence is not known in India. Reported incidence is 1 in 12,000 but in the Southern part of India, the disorder seems to be more prevalent giving an incidence as high as 1:2750.^[8,20] The diagnosis of classic CAH can be made at birth based on ambiguous genitalia in a newborn female or during the neonatal period in both sexes based on salt wasting crisis. Elevated 17 OHP indicates a possibility of CAH. The goal of classic CAH-NBS is early detection of the severe salt wasting form, therefore, prevention of adrenal crisis or death.

Galactosemia, caused by the deficiency of the enzyme Galactose-1-phosphate uridyl transferase, has an incidence of 1:30,000–1:60,000 in western countries.^[21] Not much is known about the incidence of this disease in India but it is reported to account for up to 4% of children presenting with neonatal cholestasis syndrome in India.^[22] NBS for galactosemia can be done by screening either galactose or galactose-1-phosphate levels in dried blood spots. Confirmatory testing requires enzyme analysis and may be followed by mutation studies. It is very essential to diagnose this disorder early in neonatal period as if untreated it may lead to severe life threatening episodes, affecting liver. If diagnosed early, it can be simply treated by omitting galactose from diet.

Biotinidase deficiency is a rare but easily treatable disorder caused by mutations in the BTD gene. Biotin which is a cofactor for several carboxylases involved in branched chain amino acid metabolism and fatty acid metabolism is recycled by the enzyme biotinidase. The deficiency may cause seizures, immune system impairment, hearing loss, mental retardation, coma, and even death. Other symptoms include apnea, tachypnea, hyperventilation, skin rashes, and alopecia. Later developmental delays, speech problems, ataxia, and hearing problems may occur. Onset of this disease is around 3–6 months of age and hence if it is detected early by NBS, treatment can be started prior to onset of symptoms. Patients with late or no treatment can manifest with permanent neurologic sequelae and hearing loss. Screening for disorder is done as a part of NBS programs in many countries and is a simple colorimetric determination. All positive tests are confirmed by a quantitative assay in serum and also may be confirmed by mutation analysis.

Fatty acid oxidation defects are now being included in NBS programs worldwide. This is a group of disorders with an estimated combined incidence of 1:9,000. Benefits have been proven the most in cases of MCAD deficiency and VLCAD deficiency by NBS for FAODs. Most FAODs are identified by Tandem Mass Spectrometry (TMS or MS/MS). Furthermore, they are treated by simple avoidance of fasting in most cases, whereas metabolic decompensation can be fatal in unsuspected patients. Due to these reasons, FAODs have been included in most NBS program since the mid-1990s.^[23] In 2006, the ACMG determined 5 core conditions to be included in a standardized NBS menu. These five conditions were MCAD, VLCAD, LCHAD, CTD, and CPTII.^[24] The true incidence in India is not known, however, ICMR multi-centric study has suggested a high incidence of MCAD.^[25]

LABORATORY WORKFLOW AND MANAGEMENT IN A NBS LAB

A typical NBS laboratory receives approximately 100 to 1000 dried blood spots for analysis per day. The general turnaround time for analysis and reporting is usually 2–4 working days as in some diseases treatment must be started rapidly to prevent irreversible damage. For positive results, confirmatory tests are needed. The NBS laboratory also should implement quality management system. This must be in place to ensure the system’s integrity in all phases – pre-analysis, analysis, and post- analysis. NBS laboratories are also a part of several activities such as education, public awareness, training, diagnosis, systematic follow-up, parental counseling, data management, and publications.

IMPORTANCE OF NBS

In a recent study, it was shown that only 2% of cases detected by NBS had clinically severe outcomes compared to 42% of those detected clinically.^[41] Clinically, diagnosed patients with several of the disorders have poorer outcomes than those with the same disorders identified by eNBS, including death, organ transplantation, poor developmental outcomes, and intellectual disabilities. Significantly better outcomes are seen in NBS detected patients when compared to clinically diagnosed patients.^[41-44] Documented positive outcomes are in terms of lesser intellectual disabilities,^[45] better IQs,^[41] fewer deaths, and fewer disabilities.^[42] Hence, NBS should be adopted as a policy in all countries to reduce the burden of individuals diagnosed with IEMs and other conditions. This will not only help in saving the cost for treatment and hospitalizations needed frequently in these disorders but also reduce the parental stress and anxiety, improving the quality of life for the patient and the family.

INDIAN SCENARIO

At present, there is no national NBS program in India. There is no doubt that NBS can save life, but NBS has not been accepted yet as a governmental policy in India. There is no comprehensible national strategy for implementation of a universal screening program and no guidance on which disorders should be included in the screening panel. Realizing the importance of NBS, ICMR in 2008 launched a pilot multi-center NBS program to screen 100,000 newborns for CH and CAH in 5 metropolitan cities – Chennai, Delhi, Hyderabad, Kolkata, and Mumbai. This study demonstrated the feasibility of NBS in Indian metropolitans.^[25] In 2011, the national neonatology forum recommended CH, CAH, and G6PD as the screening panel to implement for NBS in India.^[46] Many small scale or pilot projects were started in India. However, of note among these were the Chandigarh Program, Kerala State NBS program, and Goa NBS Program. Union territory of Chandigarh started NBS for CH, CAH, and G6PD in 2007.^[8] In 2008, Goa introduced mandatory expanded NBS for all newborns.^[7] In 2009, West Bengal and in 2011 Gujarat governments have approved o launch large scale NBS program. However, these programs remain yet to be implemented. Now many private hospitals and labs offer this facility although at a cost and there is no insurance or government funding for this.

About 27 million babies are born every year in our country. Approximately 4:1000 and 5:1000 are estimated to have hearing defects and congenital heart abnormalities, respectively, whereas the incidence of IEMs in India is estimated to approximately 1:1000. This high incidence is due to high prevalence of consanguinity in our country. IEMs comprise approximately 15% of total admissions in NICUs annually. If undiagnosed and untreated many children develop mental retardation, learning disabilities, autism, dyslexia, behavioral abnormalities, and scholastic backwardness later in life. There is also considerable burden – financial and emotional on the parents to diagnose, treat, and manage these children. The most rational and cost-effective way of preventing such tragedies would be to have a NBS program which will detect most of the preventable or treatable, if not all IEMs and other disorders. Awareness of benefits of NBS is increasing and this could lead to the creation of one national NBS program. Although universal screening is a cost-intensive program, the benefits outweigh the cost as it helps in reducing the mortality and morbidity in these diseases.

CONCLUSION

All hospitals in urban areas in India should initiate NBS at least for the common disorders: CH, CAH, and G6PD deficiency. Expanded newborn screening may follow once these programs are well established and necessary infrastructure is in place. There is also a need to train more physicians in IEMs before expanded NBS is started.