A Comprehensive Overview of the Developments of Cdc25 Phosphatase Inhibitors.

Cdc25 phosphatases have been considered promising targets for anticancer development due to the correlation of their overexpression with a wide variety of cancers. In the last two decades, the interest in this subject has considerably increased and many publications have been launched concerning this issue. An overview is constructed based on data analysis of the results of the previous publications covering the years from 1992 to 2021. Thus, the main objective of the current review is to report the chemical structures of Cdc25s inhibitors and answer the question, how to design an inhibitor with better efficacy and lower toxicity?

Prospective Comparison of Subtalar Arthroereisis With Calcaneal Lengthening in the Management of Planovalgus Feet of Ambulatory Children With Spastic Cerebral Palsy?

BACKGROUND: Pes planovalgus (PPV) deformity is common among cerebral palsy (CP) patients. There is no true consensus about the best way of treating this common deformity, especially when surgical interference is required. Treatment options range from orthotics to complex surgical procedures. The purpose of this prospective study was to evaluate and compare the effectiveness of 2 different procedures in the correction of symptomatic flexible PPV in ambulatory CP patients. METHODS: A total of 57 feet in 35 patients were divided into 2 groups: group 1, subtalar arthroereisis group, using the calcaneostop technique; group 2, lateral column lengthening group, using Evans osteotomy. Patients were assessed clinically by the clinical score proposed by Yoo et al and radiologically by measuring 7 weight-bearing angles, both preoperatively and 12 months postoperatively. Patients' (or parents') satisfaction and their tolerance to braces or shoes were assessed 12 months after surgery as secondary outcome parameters. RESULTS: There was a statistically significant improvement in both primary and secondary outcome parameters after both procedures in comparison to the preoperative parameters. No statistically significant differences were observed between the 2 groups regarding the outcomes of both procedures except for the greater power of arthroereisis in the correction of hindfoot valgus, which was statistically significant both clinically and radiographically. CONCLUSION: Both procedures are valid options for the surgical management of PPV in ambulatory children with spastic CP. The less-invasive nature and lower potential morbidity suggest that judicious use of arthroereisis is appropriate for some patients, especially in the context of single-event multilevel surgery. LEVELS OF EVIDENCE: Level II: Prospective, comparative study.

Treatment of genu valgum by a novel percutaneous transverse metaphyseal osteotomy of the distal femur in children and adolescents.

PURPOSE: To evaluate the outcomes of a novel percutaneous medial supracondylar femoral osteotomy and above-knee cast technique in children and adolescents as a minimally invasive surgical intervention for treatment of genu valgum. METHODS: In this prospective study, 60 patients (70 knees) with a tibiofemoral angle more than 15° were treated with a novel medial percutaneous supracondylar femoral osteotomy and above-knee cast and followed up for an average of 29 months. The radiological outcome was measured with MAD, TFA, and mLDFA. The functional outcome was evaluated by a modified Böstman score. RESULTS: The preoperative mean MAD, TFA, and mLDFA were 2.9 cm, 16.3°, and 79.2° respectively. The Böstman score averaged preoperatively 23.1. There was a significant improvement of all radiological and clinical outcome measures (P < 0.001). Per Böstman score, 2 knees in one patient (3%) showed an unsatisfactory result, while 14 (20%) and 54 (77%) knees had a good or excellent result, respectively. Two patients (three limbs) needed early re-casting. Other complications were not encountered. CONCLUSION: In experienced hands, percutaneous transverse metaphyseal femoral osteotomy and above-knee casting appear to be a safe, supracondylar cost-effective, and reliable minimally invasive acute correction technique in genu valgum in children and adolescents. LEVEL OF EVIDENCE: Level IV-therapeutic.

Cardenolides and pentacyclic triterpenes isolated from Acokanthera oblongifolia leaves: their biological activities with molecular docking study.

Pentacyclic triterpenes and cardenolides were isolated from Acokanthera oblongifolia leaves. Their chemical structures were determined based on comprehensive 1D and 2D NMR spectroscopy. Their MIC was determined against 12 microorganisms. Their exerted cytotoxicity on the immortalized normal cells, hTERT-RPE1 was assessed by the sulforhodamine-B assay. The viral inhibitory effects of compounds against Newcastle disease virus (NDV) and H5N1 influenza virus IV were evaluated. Four in vitro antioxidant assays were performed in comparison with BHT and trolox and a weak activity was exhibited. Acovenoside A was with potent against H5N1-IV and NDV with IC50 ≤ 3.2 and ≤ 2.1 µg/ml and SI values of 93.75 and 95.23%, respectively, in comparison to ribavirin. Its CC50 record on Vero cells was > 400 and 200 µg/ml, respectively. Acobioside A was the most active compound against a broad range of microbes while Pseudomonas aeruginosa was the most sensitive. Its MIC (0.07 µg/ml) was 1/100-fold of the recorded CC50 (7.1 µg/ml/72 h) against hTERT-RPE1. The molecular docking of compounds on human DNA topoisomerase I (Top1-DNA) and IV glycoprotein hemagglutinin were studied using MOE program. This study has introduced the cardenolides rather than triterpenoids with the best docking score and binding interaction with the active site of the studied proteins.

Phytochemical and antimicrobial investigation of the leaves of five Egyptian mango cultivars and evaluation of their essential oils as preservatives materials.

The sterols, hydrocarbons and fatty acids constituents of the leaves of five mango cultivars locally implanted in Egypt were identified. The effect of their essential oils (EOs) against food borne microorganisms was studied as preservative materials. The chemical constituents of the EOs isolated from mango leaves were identified by Gas Chromatography-Mass spectrometry (GC-MS) technique. Trans-caryophyllene, α-humulene and α-elemene were identified as terpene hydrocarbons, while 4-hydroxy-4-methyl-2-pentanone as oxygenated compounds were recorded in all tested cultivars with variable amounts. Results showed that Staphylococcus aureus and Escherichia coli were the most sensitive microorganisms tested for Alphonso EOs. On the other hand, Salmonella typhimrium was found to be less susceptible to the EOs of the studied cultivars. The EOs of different mango cultivars induced a steady decrease in the activity of amylase, protease and lipase at the minimum inhibitory concentration (MIC). The treatment of the tested bacteria with the EOs of mango cultivars caused a steady loss in enterotoxins even when applied at the sub-MIC. Bacteria-inoculated apple juice treated with minimum bactericidal concentration of Alphonso oil was free from the bacteria after 5 days of incubation at 25 °C. Eighteeen volatile compounds were found to reduce the activity of the amylase enzyme and the most active was cedrelanol (-7.6 kcal mol-1) followed by alpha-eudesmol (-7.3 kcal mol-1) and humulene oxide (-7 kcal mol-1). The binding mode of both of cedrelanol and alpha-eudesmol with amylase enzyme was illustrated.

In vitro chemotherapeutic and antiangiogenic properties of cardenolides from Acokanthera oblongifolia (Hochst.) Codd.

Acovenoside A (Acov-A) and acobioside A (Acob-A) were isolated from Acokanthera oblongifolia. Their anticancer properties were explored regarding, antiproliferative and antiangiogenic activities. The study included screening phase against six cancer cell lines followed by mechanistic investigation against HepG2 cancer cell line. The sulforhodamine-B (SRB) was used to determine their growth inhibitory power. In the other hand, flow cytometry techniques were recorded the cell death type and cell cycle analysis. The clonogenic (colony formation) and wound healing assays, enzyme-linked immunosorbent assay (ELISA) and molecular docking, were performed to evaluate the antiangiogenesis capability. Both compounds were strongly, inhibited four cancer cell lines at GI50 less than 100 nM. The in vitro mechanistic investigation against HepG2 resulted in cell accumulations at G2M phase and induction of apoptosis upon treating cells separately, with 400 nM Acov-A and 200 nM Acob-A. Interestingly, the same concentrations were able to activate caspase-3 by 7.2 and 4.8-fold, respectively. Suppressing the clonogenic capacity of HepG2 cells (20 and 40 nM) and inhibiting the migration of the colon Caco-2 cancer cells were provoke the results of vascular endothelial growth factor receptor2 (VEGFR2) kinase enzyme inactivation. The docked study was highly supportive, to the antiangiogenic approach of both cardenolides. The isolated cardenolides could orchestrate pivotal events in fighting cancer.

Development, synthesis, and biological evaluation of sulfonyl-α-l-amino acids as potential anti-Helicobacter pylori and IMPDH inhibitors.

Inosine 5'-monophosphate dehydrogenase (IMPDH) catalyzes a crucial step in the biosynthesis of DNA and RNA, and it has been exploited as a promising target for antimicrobial therapy. The present study discusses the development and synthesis of a series of sulfonyl-α-l-amino acids coupled with the anisamide scaffold and evaluates their activities as anti-Helicobacter pylori and IMPDH inhibitors. Twenty derivatives were synthesized and their structures were established by high-resolution mass spectrometry and 1 H and 13 C nuclear magnetic resonance measurements. Four compounds (6, 10, 11, and 21) were found to be the most potent and selective molecules in the series with minimum inhibitory concentration (MIC) values <17 µM, which were selected to test their inhibitory activities against HpIMPDH and human (h)IMPDH2 enzymes. In all tests, amoxicillin and clarithromycin were used as reference drugs. Compounds 6 and 10 were found to have a promising activity against the HpIMPDH enzyme, with IC50 = 2.42 and 2.56 µM, respectively. Moreover, the four compounds were found to be less active and safer against hIMPDH2 than the reference drugs, with IC50 > 17.17 µM, which makes sure that their selectivity is toward HpIMPDH and reverse to that of amoxicillin and clarithromycin. Also, the synergistic antibacterial activity of compounds 6, 10, amoxicillin, and clarithromycin was investigated in vitro. The combination of amoxicillin/compound 6 (2:1 by weight) exhibited a significant antibacterial activity against H. pylori, with MIC = 0.12 µg/ml. The molecular docking study and ADMET analysis of the most active compounds were used to elucidate the mode-of-action mechanism.

Configuration and molecular structure of 5-chloro-N-(4-sulfamoylbenzyl) salicylamide derivatives.

A systematic study on sulfonamide derivatives with salicylamide core is presented for possible use in pharmaceutical applications. The molecular structure of eight different compounds has been investigated by FTIR in the frequency range 4000-400 cm-1 to recognize the possible geometrical shape of the molecules needed to uniquely identify the activity of molecule in cancer cell. The electronic charge distribution of these different compounds is further illustrated by UV-Vis spectroscopy in the frequency range 190-1100 nm. The theoretical results obtained from molecular modeling calculations showed that the hydrogen bonds between the OH, CO, NH, and/or CH groups vary from one compound to the other regarding their number and bond length. This confirms the experimental FTIR results regarding the position and broadening of the OH and NH groups due to free rotation of the amide group because of changing the compounds structure by adding different groups to the last phenyl ring. The hydrogen bonds take different directions and values from one compound to the other, which seems to be the most important factor regarding the activity of these different compounds in cancer cell. Both theoretical molecular modeling calculations and FTIR experimental results have strongly evaluated the relation between the chemical structure of 5-chloro-N (4-sulfamoylbenzyl) salicylamide derivatives and their biological activities.

Synthesis and biological evaluation of novel 5-chloro-N-(4-sulfamoylbenzyl) salicylamide derivatives as tubulin polymerization inhibitors.

A novel series of sulfonamide derivatives, coupled with a salicylamide scaffold, was designed and synthesized. The structures of the synthesized compounds were established using 1H NMR, 13C NMR and high-resolution mass spectroscopy. The synthesized compounds were tested in vitro against five types of human cell lines. Two were breast adenocarcinoma, including the hormone-dependent MCF-7 and the hormone-independent MDA-MB-231. The others were the colorectal adenocarcinoma Caco-2, the carcinoma HCT-116 and the immortalized retinal-pigmented epithelium, hTERT-RPE1. Nine sulfonamides were able to inhibit the growth of the four tested cancer cells. Compound 33 was the most active against the selected colon cancer (Caco-2 and HCT-116) subtypes, while compound 24 showed the best efficacy against the examined breast cancer (MCF-7 and MDA-MB-231) cells. The selectivity index introduced compounds 24 and 33 as having the best selectivity among the breast and colon subtypes, respectively. In vitro tubulin polymerization experiments and flow cytometric assays showed that compounds 24 and 33 led to cell cycle arrest at the G2/M phase in a dose-dependent manner by effectively inhibiting tubulin polymerization. Furthermore, the results of the molecular docking studies indicate that this class of compounds can bind to the colchicine-binding site of tubulin.

Structure and absolute configuration of some 5-chloro-2-methoxy-N-phenylbenzamide derivatives.

The absolute configuration of 5-chloro-2-methoxy-N-phenylbenzamide single crystal [compound (1)] and the effect of introducing -[CH2]n-, n=1,2 group adjacent to the amide group [compounds (2) and (3)], were studied. Furthermore, the replacement of the methoxy group with a hydroxy group [compound (4)] was defined. Proton and carbon-13 NMR spectrometer were used to record the structural information of the prepared compounds. X-ray single crystal diffractometer were used to elucidate the 3D structural configurations. Intensity data for the studied compounds were collected at room temperature. The X-ray data prove that compound (1) is almost planar, with maximum r.m.s. deviations of 0.210(3)Å corresponds to C13. This planarity starts to disturb by adding -[CH2]n-, n=1,2 groups between the NH group and the phenyl ring in compounds (2) and (3), respectively. By replacing the OCH3 group by an OH group in compound (4), the plane of the chlorophenyl moiety is nearly perpendicular to that of the phenyl ring. Such new structural configurations were further illustrated by the infrared, and ultraviolet-visible spectroscopy measurements in the frequency range 400-4000cm-1 and 190-1100nm, respectively. Spectroscopic analyses were verified with the help of molecular modeling using density functional theory. The estimated total dipole moment for the prepared compounds reflects its ability to interact with its surrounding molecules. The higher dipole moment for a given structures is combined with the higher reactivity for potential use in medicinal applications.

Four butyrolactones and diverse bioactive secondary metabolites from terrestrial Aspergillus flavipes MM2: isolation and structure determination.

The chemical constituents and biological activities of the terrestrial Aspergillus flavipes MM2 isolated from Egyptian rice hulls are reported. Seven bioactive compounds were obtained, of which one sterol: ergosterol (1), four butyrolactones: butyrolactone I (2), aspulvinone H (3), butyrolactone-V (6) and 4,4'-diydroxypulvinone (7), along with 6-methylsalicylic acid (4) and the cyclopentenone analogue; terrien (5). Structures of the isolated compounds were deduced by intensive studies of their 1D & 2D NMR, MS data and comparison with related structures. The strain extract and the isolated compounds (1-7) were biologically studied against number of microbial strains, and brine shrimp for cytotoxicity. In this article, the taxonomical characterization of A. flavipes MM2 along with its upscale fermentation, isolation and structural assignment of the obtained bioactive metabolites, and evaluate their antimicrobial and cytotoxic activities were described.

Mixed medullary-follicular carcinoma of the thyroid: diagnostic dilemmas in fine-needle aspiration cytology.

Mixed medullary-follicular carcinoma (MMFC) of thyroid is an extremely rare tumor, characterized by coexistence of morphological and immunohistochemical features of both medullary carcinoma and follicular (or papillary) carcinoma. We herein present fine needle aspiration (FNA) findings of a histology-confirmed MMFC along with a review of literature. The patient was a 64-year-old woman who had a history of Hashimoto's thyroiditis and presented with enlargement of preexisting right thyroid nodule. An US-guided FNA of the thyroid nodule was performed and conventional smears were prepared. A cytologic diagnosis of "positive for malignancy, consistent with medullary thyroid carcinoma (MTC)" was rendered based on the presence of features characteristic for MTC, and the absence of components of follicular neoplasm (adenoma and carcinoma) or papillary carcinoma. However, microscopic examination of the follow-up total thyroidectomy specimen with the aid of immunocytochemical study detected minor portion of follicular carcinoma in addition to MTC. A histologic diagnosis of MMFC was then established. While specific identification of MMFC by FNA may be difficult, it should be emphasized that adequate sampling in conjunction with the proper immunostaining panel could have highlighted the different aspects of the mixed tumor.

Synthesis of some novel D-glucuronic acid acetylated derivatives as potential anti-tumor agents.

A structurally diverse series of Δ(4,5) -uronamide derivatives have been chemically synthesized starting from D-glucuronic acid itself by means of acetylation, activation, amide bond formation and base-catalyzed elimination protocols. Structure elucidation for all products along with optimization of the synthetic steps is described. The synthesized compounds were evaluated for their in-vitro anti-tumor activity against MCF-7, TK-10 and UACC-62 cell lines. The compounds 5, 11, 13, 15 and 16 were the most active against TK-10 cell line. On the other hand, the most active compounds against the MCF-7 cell line were 11 and 15. However, compounds 5, 7, 11, 13, 15 and 16 were the most active against the UACC-62 cell line.

The epithelioid blue nevus: A rare intraoral nevomelanocytic tumor.

The epithelioid blue nevus (EBN) is considered a cutaneous marker of the Carney complex. Sporadic EBN has been reported in patients not exhibiting the Carney complex. The EBN does not exhibit unique clinical features that help to differentiate it from other lesions and is often provisionally diagnosed as an acquired melanocytic nevus, or a malignant melanoma. A 52-year-old African-American female had a 3-4 mm bluish macule of the left anterior hard palate. An excisional biopsy was performed to rule out an incipient melanoma. Formalin-fixed, hematoxylin and eosin-stained sections were examined microscopically. On the basis of histopathological features, a diagnosis of EBN was rendered. We document a case of the rare EBN affecting the oral mucosa. The patient did not exhibit any features associated with the Carney complex. Two years post-operatively, there is no evidence of a recurrent tumor.

Design, synthesis and antitumor activity of novel D-glucuronic acid derivatives.

A series of D-glucuronic acid derivatives were chemically synthesized including acetylated and deacetylated glucuronamides, as well as N-glucuronides starting from the D-glucuronic acid itself by means of protection/deprotection, activation and condensation protocols. Structure elucidation of all products along with optimization of the synthetic steps is described. The synthesized compounds were evaluated for their in vitro antitumor activity against MCF-7, TK-10 and UACC-62 cell lines. The compounds 4, 5, 7, 8, 14, 16 and 18 were the most active against TK-10 cell line. On the other hand, the most active compounds against the MCF-7 cell line were 9, 18 and 20. However, compounds 7-10 13-15 and 17 were the most active against the UACC-62 cell line.

Double column osteotomy for correction of residual adduction deformity in idiopathic clubfoot.

INTRODUCTION: Adduction of the forefoot is the most common residual deformity in idiopathic clubfoot. The 'bean-shaped foot', which is a term used to describe a clinical deformity of forefoot adduction and midfoot supination, is not uncommonly seen in resistant clubfoot. SUBJECTS AND METHODS: Fifteen children (20 feet) with residual forefoot adduction in idiopathic clubfeet aged 3-7 years were analyzed clinically and radiographically. All of the cases were treated by double column osteotomy (closing wedge cuboid osteotomy and opening wedge medial cuneiform osteotomy) with soft tissue releases (plantar fasciotomy and abductor hallucis release), to correct adduction, supination and cavus deformities. Pre-operative measurements of certain foot angles were compared with their corresponding postoperative values. RESULTS: A grading system for evaluation of the results using a point scoring system was suggested to evaluate accurately both clinical and radiographic results after a follow-up period of an average of 2.3 years. Eight feet (40%) had excellent, eight (40%) good, three (15%) fair, and one (5%) poor outcome. There was no major complication. There was significant improvement in the result (P > 0.04). CONCLUSIONS: Double column osteotomy can be considered superior to other types of bone surgeries in correction of residual adduction, cavus and rotational deformities in idiopathic clubfoot.

Podoplanin is a useful marker for identifying mesothelioma in malignant effusions.

The diagnosis of malignant mesothelioma in serosal effusions continues to be a major challenge because some of its cytomorphological features closely resemble adenocarcinomas. Immunohistochemistry is a valuable tool in the differentiation of epithelioid mesothelioma from metastatic adenocarcinomas. However, no single antibody has demonstrated absolute sensitivity or specificity. In this study, we evaluated the value of immunostaining pattern for podoplanin to differentiate mesothelioma from adenocarcinomas of various origins.Cell blocks from previously collected paraffin-embedded cell blocks of 86 effusions (18 mesothelioma, 35 reactive mesothelium, 9 breast adenocarcinoma, 14 ovarian adenocarcinoma, and 10 lung adenocarcinoma) were retrieved from the file of the Department of Pathology at University of Michigan and Lund University in Sweden and were used for the study. Slides prepared from the cell blocks were stained for podoplanin. The percentage of immunostained cells was recorded as follows: 1+ (5-25%), 2+ (26-50%), and 3+ (>50%). A stain result involving <5% of cells was considered negative. The intensity of positive results was evaluated as strong, moderate, or weak.Podoplanin is expressed in 94% of malignant mesothelioma cases (17/18), 97% (30/31) of cases of reactive mesothelial, 0% of lung adenocarcinoma cases (0/9), 0% of breast adenocarcinoma (0/9), and 7% of ovarian adenocarcinoma (1/14). All positive cases of malignant mesothelioma and reactive mesothelium showed strong membranous reactivity to podoplanin. The one positive case of ovarian adenocarcinoma showed a weak membranous podoplanin immunostaining.On the basis of our results and published data, we believe that membranous podoplanin immunoreactivity, in conjunction with calretinin, would be more specific than CK5/6 and WT-1 in differentiating epithelioid malignant mesothelioma from adenocarcinoma of the lung, breast, and ovary.

Characteristics of patients with congenital clasped thumb: a prospective study of 40 patients with the results of treatment.

PURPOSE: Congenital clasped thumb is a deformity that is associated with heterogeneous congenital anomalies and it has been addressed in many congenital syndromes. The aim of this study was to diagnose and evaluate cases of clasped thumb as regards the associated congenital anomalies and syndromes, and evaluation of the results of treatment of such cases. METHODS: A prospective study on 40 patients with 73 clasped thumbs was done. All the patients' data regarding their personal, family, pregnancy and developmental histories were recorded. All the patients were exposed to thorough clinical and radiological examination and genetic assessment. The cases were classified using the Tsuyuguchi et al. (J Hand Surg [Am] 10:613-618, 1985) classification into three types. Conservative treatment was adopted in ten hands, and surgical treatment was performed for 28 hands in 17 patients, with an average follow-up of 26 months. RESULTS: Positive consanguinity was recorded in 57.5% of cases. Associated anomalies were recorded in 77.5% of cases. Type I was the most common one, followed by type III and then type II. Conservative treatment is effective in type I cases when presented early, and all patients were satisfied with the results of surgical treatment. CONCLUSIONS: We reported associated anomalies which are to our knowledge have not mentioned before in the literature which include; congenital blindness, radial deviation of the index finger and ventricular septal defect. We found that 68% of the patients had associated syndromes, and this has not been mentioned before. In this study, we found that there were no difference between type II and type III clasped thumb as regards the pathological findings, severity, the operative procedures, the treatment protocol and the operative results. Properly planned treatment gives satisfactory results.

Surgery versus surgery plus pamidronate in the management of osteogenesis imperfecta patients: a comparative study.

The aim of this study was to evaluate the efficacy of pamidronate in the management of osteogenesis imperfecta patients. This study was carried out in two groups. The first was treated only surgically whereas the second was treated by a combined approach, medical and surgical. Forty patients, divided into two groups, were surgically treated in order to correct bony deformities secondary to osteogenesis imperfecta. Group 1: twenty patients were operated at an average age of 6.5 years. Nine were type I, five type III and six type IV. Group 2: this group consisted of 20 patients to whom intermittent intravenous pamidronate were given at regular intervals for an average of 2 years postoperatively. The average age at surgery was 8.5 years. Four patients were type I, six type III, eight type IV, one type V and the remaining one type VII. The results were assessed according to a scoring system suggested and used by the authors since 1999. Group 1: we had three good, nine fair and eight poor results. Group 2: we had 11 excellent, four good and five fair results. The Bone mineral dens (BMD) increased by an average of 35.2% (22.7-112%), and the rate of refracture decreased. Best results in the management of patients can be obtained through the combined approach (surgical and medical treatment). We now advise preoperative and postoperative pamidronate for these patients.

Measurement of inaccuracy and imprecision of HCG methods using dilutions of the WHO 4th IS-HCG standard and a pregnant patient's serum.

INTRODUCTION: Differences in human chorionic gonadotropin (hCG) results obtained by seven different methods were documented by analyzing dilutions of the WHO 4th International Standard (IS) and a pregnant patient's serum. MATERIALS AND METHODS: Biases of +30.9 to -37.5% and +36.8 to -36.1% from the target concentration were found for the WHO 4th IS and patient sample dilutions, respectively. RESULTS: Imprecision was calculated from replicate measurements of hCG on the different sample dilutions. Imprecision ranged from 1.0% to 18.9% and 1.1% to 5.3% for the WHO 4th IS and patient sample dilutions, respectively. Using a maximum allowable error of 12.5% for hCG measurements, we found that two instruments were so biased that their hCG measurements could not be interchanged with hCG values produced by any of the other systems. DISCUSSION: It is ideal to use only one hCG methodology for the serial monitoring of hCG; otherwise, hCG methods should be carefully chosen to minimize inter-method bias.