Serum Biotinidase Activity Research Articles

Diagnosis and Treatment of Newborns Referred to the Metabolism Department From the National Newborn Screening Program in Türkiye: A 5-Year Single-Center Experience

Objective: The aims of this study were to investigate biochemical and genetic tests and treatment plans of newborns referred to our center with inherited metabolic disorders screened in Türkiye National Newborn Screening Program (NNSP). Material and Methods: The medical records of babies referred by the NNSP between January 2019 and November 2023 were scanned retrospectively. Plasma biotinidase activity and the biotinidase gene (BTD) analysis results for suspected biotinidase deficiency (BD), the plasma phenylalanine and phenylalanine hydroxylase gene (PAH) analysis for a suspicion of phenylketonuria (PKU) were documented with treatment information. Results: A total of 143 babies, 78 (54.5%) with suspected BD and 65 (45.5%) with suspected PKU were included. A PAH gene analysis was performed on 23 (35.4%) of those had high plasma phenylalanine levels, among which 86.9% were identified with the biallelic variant. Five patients were started on sapropterin-diet combined therapy, three on diet therapy and one on sapropterin therapy. In the first serum biotinidase activity measurement of babies referred with suspected BD, a heterozygous deficiency was detected in 48.7%, partial deficiency in 39.7% and profound deficiency in 10.3%. A BTD gene analysis was performed on 79.5% of those with suspected BD, and biallelic variants were detected in 50%. Forty-six patients (59.0%) underwent biotin treatment. Conclusion: In our study, approximately one-third of the babies referred from NNSP over the five-year course of the study had biallelic variants of the relevant disease. Our research is one of the few studies on NNSP in our country and presents the diagnosis and treatment process of PKU and BD.

Accurate determination of Biotinidase activity in serum by HPLC and its utilization as second tier test for the confirmation of initial positive newborn screening results

Diagnosis of Biotinidase deficiency (BTD) is extremely important to avoid several neurodevelopmental problems in early childhood. Colorimetric and fluorometric methods lack specificity and selectivity due to several interferences resulting in a high number of false positive results. We developed an HPLC method for BTD activity in serum with fluorescent detection. In colorimetric assays, biotinidase attacks the amide linkage of the artificial substrate biotinidyl-4-aminobenzoic acid (B-PABA) and releases p-aminobenzoic acid (PABA), which is converted to a purple dye by diazotization reaction. The newly developed method injects the reaction mixture directly into the HPLC column and quantifies using a six-point calibration curve without coupling and diazotization reaction. The method is linear over the 5–1000 μmol/L range. The detection and quantitation limits were 2.5 μmol/L and 5.0 μmol/L, respectively. When compared with colorimetric assay, the correlation coefficient (R2) was 0.9963. The within-assay and between-assay precision was <10.0% for four levels of quality control samples. No significant variation in BTD activity was detected due to hemolysis, icteric, and lipemic samples. The newly developed method eliminates the potential interference due to the presence of aromatic amines and significantly reduces the false positive results observed with the colorimetric method. It is simple, specific, sensitive, faster in sample preparation, and requires a small sample volume. The newly developed HPLC method was used in our laboratory as a secondary tier test for initial positive BTD samples from newborn screening programs. To our knowledge, no similar HPLC method has been reported to date.

Analysis of Biotinidase Activity in Serum by Digital Imaging Colorimetry Detection.

Biotinidase deficiency (BD) is an autosomal recessive inherited disorder of biotin recycling that leads to neurological and cutaneous consequences if left untreated. The clinical features of BD can be ameliorated or prevented by the administration of pharmacological doses of the vitamin biotin. Since it is a treatable disorder, BD is included in the newborn screening program in Türkiye as in many other countries. Therefore, monitoring of biotinidase enzyme activity (BEA) is of vital importance, especially for patients. The aim of this study was to develop a simple and reliable colorimetric method based on digital imaging for the analysis of BEA in serum samples. To determine the optimum distance and LED light source in the analyzer box that we fabricated in the laboratory, images of the solutions in a 96-well microplate were taken with a mobile phone camera, and each color space was examined. The most reliable relationship was between blank subtracted intensities of green channel and analyte concentrations, which was in the range of 35-400 ng/mL p-aminobenzoic acid (r2 = 0.999). The limit of detection and limit of quantification were 11 and 35 ng/mL, respectively. The proposed method was successfully applied to serum samples of 60 patients with BD and 60 healthy controls. We claim that the method can be easily performed for determination of BEA anywhere without needing expensive instruments.

Tetraparesis as an initial manifestation of biotinidase deficiency: a case report.

The authors present a case of 2.5-year-old boy complained of progressive weakness in all four limbs, with difficulties in breathing. Abdominal examination revealed hepatomegaly and splenomegaly. Also, her parents were first-degree cousins. Therefore, tandem mass spectroscopy and urine organic acid analysis were planned to exclude metabolic disorders. Urinary organic acid analysis revealed elevated levels of methylmalonic acid and 3-hydroxyisovaleric acid. Serum biotinidase activity was found to be 3.9nmol/min/ml. Oral biotin at a dose of 1mg/kg daily was initiated. A marked improvement of his neurological deficit was noted over a period of 15 days after treatment and cutaneous manifestations resolved within 3 weeks. Myelopathy due to BTD is a challenging diagnosis. Spinal cord impairment is a rare complication of this disease and is frequently unrecognized. BTD should be included in the differential diagnosis of children presenting with demyelinating spinal cord disease.

Molecular Background and Disease Prevalence of Biotinidase Deficiency in a Polish Population-Data Based on the National Newborn Screening Programme.

Biotinidase deficiency (BD) is a rare autosomal recessive metabolic disease. Previously the disease was identified only by clinical signs and symptoms, and since recently, it has been included in newborn screening programs (NBS) worldwide, though not commonly. In Europe, BD prevalence varies highly among different countries, e.g., from 1:7 116 in Turkey to 1:75 842 in Switzerland. This paper aimed to present the molecular spectrum of BD (profound and partial forms) in Polish patients diagnosed within the national NBS of 1,071,463 newborns. The initial suspicion of BD was based on an abnormal biotinidase activity result determined in a dry blood spot (DBS) by colorimetric and by fluorimetric methods while biochemical verification was determined by serum biotinidase activity (as quantitative analysis). The final diagnosis of BD was established by serum enzyme activity and the BTD gene direct sequencing. The obtained results allowed for the estimation of disease prevalence (1:66,966 births, while 1:178,577 for profound and 1:107,146 for partial forms), and gave novel data on the molecular etiology of BD.

Evaluation of the efficiency of serum biotinidase activity as a newborn screening test in Turkey.

Biotinidase Deficiency (BD) is an autosomal recessive metabolic disorder. However, the relationship between genotype and biochemical phenotype has not been completely elucidated yet. But still, some mutations are accepted to be associated with profound or partial deficiency. We aimed to evaluate the results of biochemical enzyme activity in accordance with the presence of genetic mutations and investigate the correlation between genotype and biochemical phenotype together in the study. This retrospective study was carried out using data from medical records of 133 infants detected by the newborn screening followed by serum biotinidase activity (BA) detection with semi-quantitative colorimetric method. Mutation analysis was performed to confirm the diagnosis. In addition, the expected biochemical phenotype based on the known mutant alleles were compared with the observed biochemical phenotype. When confirmed with mutation analysis results, the diagnostic sensitivity and specificity of serum BA with spectrophotometric method was 93.1% and 95.1%, respectively. In 93.98% of the cases conformity was observed between the biochemical phenotype and the genotype. The c.1330G>C(p.D444H) and c.470G>A (p.Arg157His) were the most common allelic variants with frequencies of 63.69% and 33.75%, respectively. The diagnostic test is supposed to have a high sensitivity to identify asymptomatic BD patients. Apparently healthy cases with almost normal enzyme activity and a variant allele in the genetic analysis were reported to present symptoms under stress conditions, which should be kept in mind. This study can be accepted as an informative report as it may contribute to the literature in terms of the allelic frequency and determination of the relation between genotype and biochemical phenotype. Also, method verification including the assessment of possible effects of non-genetic factors on BA according to the certain mutation types is warranted.

Twenty-seven mutations with three novel pathologenic variants causing biotinidase deficiency: a report of 203 patients from the southeastern part of Turkey.

Biotinidase deficiency (BD) is an autosomal recessive inborn error of metabolism characterized by neurologic and cutaneous symptoms and can be detected by newborn screening. Newborn screening for BD was implemented in Turkey at the end of 2008. In total, 203 patients who were identified among the infants detected by the newborn screening were later confirmed to have BD through measurement of serum biotinidase activity. We also performed BTD mutation analysis to characterize the genetic profile. Twenty-seven mutations were identified. The most commonly found variants were c.1330G>C (p.D444H), c.1595C>T (p.T532M), c.470G>A (p.R157H), and c.198_104delGCGGCTGinsTCC (p.C33Ffs ) with allele frequencies of 0.387, 0.175, 0.165 and 0.049, respectively. Three novel pathogenic and likely pathogenic variants were identified: p.W140* (c.419G>A), p.S319F (c.956C>T) and p.L69Hfs*24 (c.192_193insCATC). We also identified three mutations reported in just one patient in the past (p.V442Sfs*59 [c.1324delG], p.H447R [c.1340A>G] and p.198delV [c.592_594delGTC]). Although all of the patients were asymptomatic under the treatment of biotin, only one patient, who had the novel c.419G>A homozygous mutation became symptomatic during an episode of acute gastroenteritis with a presentation of ketosis and metabolic acidosis. Among the screened patients, 156 had partial and 47 had profound BD. We determined the mutation spectra of BD from the southeastern part of Turkey. The results of this study add three more mutations to the total number of mutations described as causing BD.

Background History, Clinical Presentation and Laboratory Profile in Cases of Suspected Neurometabolic Disorders

Background : Neurometabolic disorders (NMD) in children may present at any age with a wide range of clinical manifestations. Unexplained or intractable seizure is one of the important associations. Consanguinity, regression of development and sibling death are the clues to suspect neurometabolic disorders when laboratory support is limited. Laboratory findings however, provide the confirmatory diagnosis which is unavailable in Bangladesh.Objectives : To determine the association of consanguinity, regression of development, seizures, EEG findings and other laboratory investigations in children suspected to have neurometabolic disorders and to aid clinicians working in resourcepoor countries.Methodology : A retrospective analysis was done from the records of the patients suspected to have neurometabolic disorders admitted in the department of Neurosciences, Dhaka Shishu Hospital, Dhaka during the period of July 2007 to February 2011. Tandem Mass Spectrometry (TMS), biotinidase activity and other enzyme assay were done through a private laboratory in New Delhi, India.Results : Total 128 children were studied and the parents of 39 (31%) had history of consanguineous marriage. Seizure was associated with 96 (75%) children and abnormal EEG findings were recorded in 83 (65%). Plasma ammonia was done in 98 cases and found to be increased in 53 (54%) cases. Plasma lactate was done in 94 cases and found high in 40 (43%). TMS were done in 111 (85%) children and abnormality were found in 70 (63%) cases. Serum biotinidase activity was advised for 41 children as per TMS result and measured in 25 children of which deficient activity was found in 17(68%); borderline in 4 (16%) and normal activity in 4 (16%) cases.Conclusion: Background history and clinical presentation followed by stepwise laboratory investigation is necessary to identify neurometabolic disorders. Early and appropriate intervention can reduce neurodisability in many situations.Bangladesh J Child Health 2015; VOL 39 (1) :24-29

Outcomes of oral biotin treatment in patients with biotinidase deficiency — Twenty years follow-up

IntroductionBiotinidase deficiency (BTD) is an inborn error of biotin metabolism inherited as an autosomal recessive trait. Due to the, biotinidase deficiency, biotin is not recycled. Individuals with BTD usually exhibit neurological and cutaneous abnormalities unless treated with biotin. Supplementation with biotin may either ameliorate or if early introduced even prevent symptoms when introduced presymptomatically. Patients and methodsSince 1991, 22 Polish patients from 19 families have been diagnosed with BTD. In 16 children the diagnosis had been suspected on the basis of clinical signs: skin lesions, hyperventilation, seizures, spasticity, and laboratory investigation (elevated lactate and metabolites on urine organic acids profile).The defect was enzymatically (serum biotinidase activity measurement) and genetically (tested for mutations in the BTD gene) confirmed afterwards. All patients were treated with biotin. Urine organic acids analysis (GC/MS) for 3-hydroxizovaleric acid was used for patients' monitoring. Neurological, audiological and ophthalmological evaluation has been conducted once a year. ResultsIn 5 symptomatic patients a progressive optic nerve atrophy had already been noted at the time of treatment initiation. In these patients sensorineural hearing loss has also been diagnosed despite biotin supplementation. Asymptomatic patients treated with biotin supplementation presented no signs or symptoms of BTD. Supplementation with biotin slows the progression of BTD in symptomatic patients, but does not reverse nerve atrophy. Nonetheless, introduction of the treatment with biotin during presymptomatic stage of the disease prevents the onset of symptoms including optic atrophy and hearing loss. Homozygosity for the p.Leu215Phe mutation in BTD gene seems to be frequent in patients from the North-Eastern region of Poland and is connected with the hearing loss. ConclusionSince the prognosis for individuals diagnosed with BTD is good, provided they are treated before symptoms occur, it is justified to add this metabolic disorder to the panel of conditions screened under the national newborn screening programme in Poland.

Biotinidase deficiency: Spectrum of molecular, enzymatic and clinical information from newborn screening Ontario, Canada (2007-2014).

Untreated profound biotinidase deficiency results in a wide range of clinical features, including optic atrophy, cutaneous abnormalities, hearing loss and developmental delay. Ontario, Canada incorporated this treatable deficiency in newborn screening over the past 8years. This study elucidates the molecular, biochemical, and clinical findings from the pilot project. Information from initial screens, serum biotinidase activity level assays, molecular testing, and family history for 246 positive newborns screens were analyzed. A mutation spectrum was created for the province of Ontario, including common mutations such as D444H, D444H/A171T, Q456H, C33fs, and R157H. Individuals with partial deficiency were separated into 3 groups: D444H homozygotes (Group 1); compound heterozygotes for D444H with another profound allele (Group 2); compound heterozygotes with two non-D444H alleles (Group 3). Biochemical phenotype-genotype associations in partial deficiency showed a significant difference in serum biotinidase activity in between any given two groups. Three children with partial deficiency discontinued biotin for varied lengths of time. Two of whom became symptomatic with abnormal gait, alopecia, skin rashes and developmental delay. A need for more congruency in diagnostic, treatment and educational practices was highlighted across the province. Heterogeneity and variation in clinical presentations and management was observed in patients with the partial deficiency.

Novel mutations causing biotinidase deficiency in individuals identified by newborn screening in Michigan including an unique intronic mutation that alters mRNA expression of the biotinidase gene

Biotinidase deficiency (BD) is an autosomal recessive disorder resulting in the inability to recycle the vitamin biotin. Individuals with biotinidase deficiency can develop neurological and cutaneous symptoms if they are not treated with biotin. To date, more than 165 mutations in the biotinidase gene (BTD) have been reported. Essentially all the mutations result in enzymatic activities with less than 10% of mean normal serum enzyme activity (profound biotinidase deficiency) with the exception of the c.1330G>C (p.D444H) mutation, which results in an enzyme having 50% of mean normal serum activity and causes partial biotinidase deficiency (10–30% of mean normal serum biotinidase activity) if there is a mutation for profound biotinidase deficiency on the second allele. We now reported eight novel mutations in ten children identified by newborn screening in Michigan from 1988 to the end of 2012. Interestingly, one intronic mutation, c.310-15delT, results in an approximately two-fold down-regulation of BTD mRNA expression by Quantitative real-time reverse-transcription PCR (qRT-PCR). This is the first report of an intronic mutation in the BTD gene with demonstration of its effect on enzymatic activity by altering mRNA expression. This study identified three other mutations likely to cause partial biotinidase deficiency. These results emphasize the importance of full gene sequencing of BTD on patients with biotinidase deficiency to better understand the genotype and phenotype correlation in the future.

Biotinidase deficiency in childhood

This study reports the clinical, laboratory profile and outcome in seven patients with biotinidase deficiency. The serum biotinidase activity was assayed using spectrophotometric analysis. The age at presentation varied from day 1 of life to the 5 th month. Seizures were the presenting complaint in six patients and clonic seizures were the predominant seizure type. Sparse hair was seen in four patients, while three did not have any cutaneous manifestation. None of the patients had acidosis or hyperammonemia. The clinical response to biotin was dramatic with seizure control in all patients. One patient had neurological deficit at follow-up, while none had optic atrophy or sensorineural hearing loss. Biotinidase deficiency, a potentially treatable condition, should be thought of in any child presenting with neurological symptoms, especially seizures, even in the absence of cutaneous or laboratory manifestations.

The first reported HLCS gene mutation causing holocarboxylase synthetase deficiency in a Vietnamese patient

Holocarboxylase synthetase deficiency is an inborn error of biotin metabolism leading to multiple carboxylase deficiency which is often biotin responsive. This disease is believed to be relatively common among the Asian population. A 6-year-old Vietnamese boy presented with recurrent episodes of severe metabolic acidosis precipitated by intercurrent illnesses. An extensive skin rash was present since the onset of his illness. Multiple carboxylase deficiency was considered a likely diagnosis based on the history and the characteristic skin rash. This diagnosis was later confirmed by urine organic acid and molecular genetic studies. Urine organic acid showed characteristic excretion of glycine conjugates. Serum biotinidase activity was normal. Sequencing of the holocarboxylase synthetase gene revealed the patient being homozygous for a common mutation R508W. The patient showed a dramatic response to biotin within days of its administration. This case illustrates a potential highly treatable inborn error of metabolism that can be recognized on clinical grounds and its favorable response to biotin treatment.

Elevated serum biotinidase activity: a new view in diagnostics of hepatic glycogenoses

Elevated serum biotinidase activity: a new view in diagnostics of hepatic glycogenoses

Development and characterization of a mouse with profound biotinidase deficiency: A biotin-responsive neurocutaneous disorder

Biotinidase deficiency is the primary enzymatic defect in biotin-responsive, late-onset multiple carboxylase deficiency. Untreated children with profound biotinidase deficiency usually exhibit neurological symptoms including lethargy, hypotonia, seizures, developmental delay, sensorineural hearing loss and optic atrophy; and cutaneous symptoms including skin rash, conjunctivitis and alopecia. Although the clinical features of the disorder markedly improve or are prevented with biotin supplementation, some symptoms, once they occur, such as developmental delay, hearing loss and optic atrophy, are usually irreversible. To prevent development of symptoms, the disorder is screened for in the newborn period in essentially all states and in many countries. In order to better understand many aspects of the pathophysiology of the disorder, we have developed a transgenic biotinidase-deficient mouse. The mouse has a null mutation that results in no detectable serum biotinidase activity or cross-reacting material to antibody prepared against biotinidase. When fed a biotin-deficient diet these mice develop neurological and cutaneous symptoms, carboxylase deficiency, mild hyperammonemia, and exhibit increased urinary excretion of 3-hydroxyisovaleric acid and biotin and biotin metabolites. The clinical features are reversed with biotin supplementation. This biotinidase-deficient animal can be used to study systematically many aspects of the disorder and the role of biotinidase, biotin and biocytin in normal and in enzyme-deficient states.

High incidence of profound biotinidase deficiency detected in newborn screening blood spots in the Somalian population in Minnesota

Newborns identified with profound biotinidase deficiency (BTD) by the Minnesota Newborn Screening Program (MN NBS) between 1 October 2004 and 30 May 2008 were all from new immigrant groups. Thirty-three positive cases of BTD were identified out of 264 727 infants screened by the Wolf colorimetric system during the period of this study by MN NBS. Five cases of profound BTD (0.1 to <0.6 nmol/min per ml) and 26 cases of partial BTD (0.9 to 2.3 nmol/min per ml) were later confirmed through measurement of serum biotinidase activity. The incidence of combined partial and profound BTD of 1/8540 and that of profound BTD of 1/52 945 in Minnesota are unusually high in comparison with the reported worldwide numbers of 1/61 067 for combined BTD and 1/137 401 for profound BTD. Four out of the 5 cases of profound BTD ascertained in the MN NBS cohort were of Somali ethnic background, and the remaining case was of Asian (Pakistani/Indian) ethnic background. All four Somali patients have the P497S mutation, with one of the four being homozygous for the mutation. The three compound heterozygotes all have a novel mutation (P142T) and two of them have another change (Y428Y) that has never been described. Within the last two decades, Minnesota has become home to an estimated 40 000 Somali immigrants and their children (<1% of the total Minnesota population). New population demographics prompt careful analysis of case cohorts to identify specific groups at risk for rare inborn errors of metabolism.

Serum Biotinidase Activity in Children Treated With Valproic Acid and Carbamazepine

There is evidence that valproic acid causes a reduction of serum biotinidase enzyme activity. We determined the serum concentration of antiepileptic drugs, transaminases, gamma-glutamyl transferase, ammonia, and biotinidase enzyme activity in 57 children treated with valproic acid, in 17 children treated with carbamazepine, and in 75 age- and sex-matched healthy controls. There were no significant differences in the serum biotinidase enzyme activity between the patients treated with valproic acid, the patients treated with carbamazepine, and the control group. Hyperammonemia was detected in 8 patients treated with valproic acid. Hair loss was observed in 3 female patients treated with valproic acid, and the alopecia disappeared with the oral administration of biotin (10 mg/ d) in 3 months. These results suggest that the treatment with valproic acid does not alter the serum biotinidase enzyme activity.

The influence of valproic acid treatment on hair and serum zinc levels and serum biotinidase activity

Some of the side effects that develop during long-term valproic acid (VPA) treatment are similar to symptoms of zinc and partial biotinidase deficiencies. This situation suggests an association between these side effects and biotinidase and/or zinc deficiencies. In 32 pediatric patients (22 females, 10 males) receiving VPA treatment, hair and serum zinc levels and serum biotinidase activity (BA) were measured prior to and in the 3rd and 6th months of treatment. Also, serum VPA levels were measured in the 3rd and 6th months of treatment. The mean serum and hair zinc levels were found to be reduced in the 3rd and 6th months of treatment as compared with the pre-treatment values, while the mean serum BA was lower than the pre-treatment values in the 3rd month of treatment, but returned to initial values in the 6th month of treatment. In the 3rd and 6th months of treatment, patients complaining about hair loss had lower hair and serum zinc levels and serum BA but greater mean serum VPA than those who did not. However, the differences between parameters were not statistically significant. Our findings suggest that hair loss in patients can be attributed to zinc and BA depletion within the first 3 months, and to zinc depletion only by the 6th month.

Elevated serum biotinidase activity in hepatic glycogen storage disorders–A convenient biomarker

An elevated serum biotinidase activity in patients with glycogen storage disease (GSD) type Ia has been reported previously. The aim of this work was to investigate the specificity of the phenomenon and thus we expanded the study to other types of hepatic GSDs. Serum biotinidase activity was measured in a total of 68 GSD patients and was compared with that of healthy controls (8.7 +/- 1.0; range 7.0-10.6 mU/ml; n = 26). We found an increased biotinidase activity in patients with GSD Ia (17.7 +/- 3.9; range: 11.4-24.8; n = 21), GSD I non-a (20.9 +/- 5.6; range 14.6-26.0; n = 4), GSD III (12.5 +/- 3.6; range 7.8-19.1; n = 13), GSD VI (15.4 +/- 2.0; range 14.1-17.7; n = 3) and GSD IX (14.0 +/- 3.8; range: 7.5-21.6; n = 22). The sensitivity of this test was 100% for patients with GSD Ia, GSD I non-a and GSD VI, 62% for GSD III, and 77% for GSD IX, indicating reduced sensitivity for GSD III and GSD IX, respectively. In addition, we found elevated biotinidase activity in all sera from 5 patients with Fanconi-Bickel Syndrome (15.3 +/- 3.7; range 11.0-19.4). Taken together, we propose serum biotinidase as a diagnostic biomarker for hepatic glycogen storage disorders.

Serum biotinidase is a sensitive and specific biochemical marker of hepatic dysfunction: A preliminary report

Biotinidase is an enzyme synthesized predominantly by the liver. Serum activity of this enzyme has been shown to be low in chronic liver disease. In this study, we endeavored to assess the diagnostic value of serum biotinidase as a marker of hepatic biosynthetic function in acute and chronic liver dysfunction. Twenty-three patients with acute liver disease and 46 with chronic liver disease, as diagnosed by clinical examination, laboratory tests, histopathology and tests for viral markers, were inducted into the study. Forty-six healthy volunteers were selected as controls. Serum biotinidase activity was estimated in all the subjects. Biotinidase activity was found to be significantly lower in the serum of patients with acute (4.59 +/- 1.26 IU/L vs 7.56 +/- 0.82 IU/L in controls; P</= 0.001) and chronic (2.98 +/- 1.18 IU/L vs 7.56 +/- 0.82 IU/L in controls; P</= 0.001) liver disease. Using receiver-operator characteristic curves, serum biotinidase was found to have high values of sensitivity and specificity when applied as a diagnostic test in both acute and chronic liver disease. These results suggest that serum biotinidase may be a sensitive and specific diagnostic marker of hepatic biosynthetic function in both acute and chronic liver disease.