Finding blunders in thyroid testing: experience in newborns.

We evaluated thyroxin (T4) and thyroid-stimulating hormone (TSH) data along with clinical information from 600,000 newborns. We looked for certain combinations of tests and clinical data that were questionable and possibly mistaken. Our approach suggests that certain combinations of test results, especially the presence of missing results deserved further evaluation for possible blunders. We found that missing tests were frequently the result of oversight. The laboratory used the well-known standard blood-spot-on-filter paper methods for TSH and T4. For quantitation of TSH and T4, we used the time-resolved fluoroimmunoassay available from Perkin Elmer. We found 56 babies with confirmed primary congenital hypothyroidism (PCH) in a total of 600,000 patients. We also found 18 sets of results in the same 600,000 babies that gave inconsistent findings, had missing values, and (or) possible misinterpretations of the clinical and (or) laboratory data. What is an acceptable mistake rate? All mistakes are unacceptable, but there is likely some irreducible mistake rate, and efforts to reduce the mistake or blunder rate still further may not be cost-effective. What can be done is to study the mistake rate per 600,000 babies from year to year; the mistake rate should be decreasing or not changing. This assumes a stable cohort of babies; an assumption that may be acceptable. We applied a form of pattern recognition to identify cases of possible blunders and missing values in either the laboratory or clinical data. What is clear is that we apparently identified some blunders. The 18 mistakes per 600,000 babies may be "very low" and acceptable. We recommend that seeking ever decreasing mistakes is the way to go, and the level of monitoring the data should be very intense given the serious consequences of mis-diagnosed thyroid disorders.

Pathophysiology and diagnostic value of urinary trypsin inhibitors.

Inflammation is an important indicator of tissue injury. In the acute form, there is usually accumulation of fluids and plasma components in the affected tissues. Platelet activation and the appearance in blood of abnormally increased numbers of polymorphonucleocytes, lymphocytes, plasma cells and macrophages usually occur. Infectious disorders such as sepsis, meningitis, respiratory infection, urinary tract infection, viral infection, and bacterial infection usually induce an inflammatory response. Chronic inflammation is often associated with diabetes mellitus, acute myocardial infarction, coronary artery disease, kidney diseases, and certain auto-immune disorders, such as rheumatoid arthritis, organ failures and other disorders with an inflammatory component or etiology. The disorder may occur before inflammation is apparent. Markers of inflammation such as C-reactive protein (CRP) and urinary trypsin inhibitors have changed our appraisal of acute events such as myocardial infarction; the infarct may be a response to acute infection and (or) inflammation. We describe here the pathophysiology of an anti-inflammatory agent termed urinary trypsin inhibitor (uTi). It is an important anti-inflammatory substance that is present in urine, blood and all organs. We also describe the anti-inflammatory agent bikunin, a selective inhibitor of serine proteases. The latter are important in modulating inflammatory events and even shutting them down.

Age-dependent cutoff values in screening newborns for hypothyroidism.

OBJECTIVES: We wanted to develop age-related reference (cutoff) values and an algorithm to identify babies at low, moderate, and high risk for hypothyroidism of any cause. We used thyroid-stimulating hormone (TSH) as the primary tool, and thyroxine (T4) as part of a confirmatory test. Our data permitted us to estimate cutoff values for newborns at <24 h, 24 to 47 h, 48 to 71 h, 72 to 95 h, and > or =96 h after birth. METHODS: We used a time-resolved fluoroimmunoassay method for TSH and T4 with the AutoDELPHIA instrument (Perkin-Elmer Life Sciences, Turku, Finland). TESTING ALGORITHM: We developed a conservative algorithm for TSH and T4 testing. In the initial screening, we used a > or =20 microIU/ml cutoff for TSH to identify those babies of any age who required confirmatory testing on a repunched filter paper blood specimen. RESULTS: In 161,244 newborns tested during 2002, we found 8,035 babies with TSH values > or =20 microIU/ml. Graphs of the values for TSH vs. age in hours revealed the possibility of using more than one cutoff value. The general finding was that the cutoff values decreased with increasing age of the newborn. CONCLUSIONS: Based on our findings, we conclude that testing babies who are <24 h old is not recommended and should only be performed if no other specimen is available. A high TSH in babies <24 h old is unreliable for screening newborns for hypothyroidism. We routinely stipulate that the infant be at least 48 h old for TSH and T4 testing. If not, the cutoff value must be set to a higher value to prevent an excessive number of false-positive results; however, this increases the chance of missing a truly hypothyroid baby. We designated newborns as being at "low" (LR), "moderate" (MR), or at "high" risk (HR) for hypothyroidism. The TSH test continues to be a screening test; and follow-up quantitative testing and clinical evaluation are needed for all babies identified as being at MR or HR for hypothyroidism. SETTING: Newborn Screening Laboratory of the Ohio Department of Health, Columbus, Ohio.

Near-patient testing for infection using urinalysis and immuno-chromatography strips.

Urinary tract infections require costly confirmatory tests such as a urine culture to establish the diagnosis. Elimination of the culture step would save resources; diagnosis and treatment could begin in hours rather than days. We tested a new dip-and-read strip that uses immuno-chromatography (IC) to detect infectious agents in urine. We used a goat-derived polyclonal antibody with reactivity to the cell-wall proteins of Escherichia coli (E. coli). Fluorescein linked to the anti-E. coli antibody served to trap the bacteria on a strip coated with an anti-fluorescein mouse antibody. Blue latex particles were linked to anti-E. coli antibodies by standard methods and were used for detection of E. coli. We found that the combination of leukocyte esterase and nitrite dipsticks gave negative predictive values of 93% for culture-negative urines, i.e., there were very few false-negative results. Using the same dipsticks on culture-positive specimens, the positive predictive values were unacceptably low; we obtained too many false-positive values. By contrast, the IC strips gave negative predictive values of 89%. The major advantage of the IC strips is that the positive predictive values were higher, i.e., there were fewer false-positive results. The combined use of both IC strips and urinalysis dipsticks offers the best strategy for diagnosing infection with dipsticks. The IC strip test could reduce the necessity of a urine culture in patients with suspected infections and provide rapid point-of-care testing.

The uristatin dipstick is useful in distinguishing upper respiratory from urinary tract infections.

BACKGROUND: We determined the diagnostic value of the trypsin inhibitor, uristatin, that is commonly found in urine and plasma in patients with infections or inflammations of any kind. METHODS: We collected urine specimens from patients with infections of the urinary or upper respiratory tract and from healthy controls. We also collected blood from patients with a likely upper respiratory tract infection and healthy controls. A bacterial count of >10(5) organisms/ml in urine was considered to represent infection rather than contamination. RESULTS: The uristatin dipstick test in urine showed acceptable negative predictive values (NPV of up to 93%) for patients without infection or inflammation. Here, the dipsticks could eliminate some urine cultures. For those with infection or inflammation, the positive predictive values (PPV) of the dipsticks were lower (up to 57%). Including the leukocyte esterase and nitrite values increased the PPV of the dipsticks for those with disease. CONCLUSIONS: The uristatin strip was more accurate than the leukocyte and nitrite dipsticks for predicting upper respiratory infections (URI) and C-reactive protein for those with infection or inflammation. The uristatin dipstick was able to detect both the bikunin and uristatin inhibitors.

Detection of low-molecular-weight proteins in urine by dipsticks.

BACKGROUND: Testing of urines with dipsticks for proteinuria, glycosuria, etc., is common practice. A deficiency with currently available dipsticks is their lack of chemical sensitivity and underestimation of low-molecular-weight proteins such as light chains. METHODS: We experimented with a number of dyes that gave an easily recognized color change on dipsticks for various low-molecular-weight proteins such as alpha-1-glycoprotein, alpha-1- and beta-2-microglobulin, and kappa and lambda light chains. We were successful in formulating a dye for impregnating dipsticks that gave a color change with low-molecular-weight proteins. RESULTS: Most dipsticks will measure proteins down to about 1 g/l. Our composite of two dyes (described here as the "TPR" dipsticks) gave reproducible results for protein concentrations of >/=300 mg/l, and detected low-molecular proteins. The TPR reagent is resistant to interferences from many compounds; also, the protein results are not altered in a given urine at a pH between 5 and 8. CONCLUSIONS: We have developed a dipstick that detects low-molecular-weight proteins. The dipsticks are easy to use and are suitable for outpatient or point-of-care testing. The precision of the dipsticks is satisfactory and is only marginally lower than quantitative spectrophotometric methods using pyrogallol red (PYR).

Clinical utility of a rapid test for uristatin.

OBJECTIVES: Uristatin is a trypsin inhibitor present in urine that is increased in most patients with bacterial or viral infections and in many with inflammatory disorders. We included the assay of uristatin as part of a screening program carried out by pediatricians on 4207 Japanese schoolchildren to judge the ability of uristatin to identify those with an infection and (or) inflammation of any cause. We used urine dipsticks for the assay of uristatin, creatinine, albumin, blood, leukocyte esterase, and protein. We also performed quantitative assays for uristatin and creatinine. Another aim was to estimate the reference range for uristatin in schoolchildren, ages 5 to 14 yr. METHODS: We prepared dipstick pads that were impregnated with a chromogenic substrate for trypsin and measured the uristatin-caused inhibition of trypsin in urine. We measured creatinine so that the ratio of uristatin to creatinine could be calculated to correct for urine concentration. RESULTS: We obtained quantitative uristatin and creatinine results for 4207 children. Of these, 177 had an abnormal urine dipstick for albumin or blood or protein or leukocyte esterase or a combination of these. We used data from 3622 children to establish the reference range for the uristatin dipsticks. The 3622 were diagnosed by their pediatricians as free from an infection or inflammation of any cause and with normal urine dipstick tests. We recommend an upper reference limit for uristatin by dipstick of < or = 7.5 mg uristatin/g creatinine. The leftover 408 children ( [4207-3622-177] = 408) fell into two groups: 205 with diagnoses of no infection, possible infection, or possible inflammatory disorders. The remaining 203 children were renal disease follow-up cases. The diagnoses were based on a physical examination, microscopic urinalysis plus urine dipstick tests for albumin, blood, creatinine, protein, leukocyte esterase and a complete blood count. In the 205 children, 46 had an abnormal uristatin dipstick test, 39 had an abnormal uristatin by immunoassay, 41 had an abnormal erythrocyte sedimentation rate (ESR), 27 had an abnormal serum C-reactive protein (CRP), and one had an abnormal urine microscopic exam. For the first 938 children in the study, the agreement was 93% of negative dipstick uristatin results and immunoassays. The agreement of positive uristatin dipsticks with immunoassays was 85%. We assumed that the immunoassay results were correct. In the evaluation of 189 children with fever, 62 also had an abnormal uristatin by dipstick. DISCUSSION: A rapid dipstick test for uristatin read on a reflectance photometer gave values that compared well with a quantitative immunoassay method. The uristatin test is sensitive but not specific for any cause of infection or inflammation. Uristatin is easy to determine and appears to be a better indicator than fever, ESR, or CRP for the diagnosis of an infection or inflammation.