Lachs M S, Nachamkin I, Edelstein P H, Goldman J, Feinstein A R, Schwartz J S
Yale University School of Medicine, New Haven, Connecticut.
Ann Intern Med. 1992 Jul 15;117(2):135-40. doi: 10.7326/0003-4819-117-2-135.
To determine if the leukocyte esterase and bacterial nitrite rapid dipstick test for urinary tract infection (UTI) is susceptible to spectrum bias (when a diagnostic test has different sensitivities or specificities in patients with different clinical manifestations of the disease for which the test is intended).
Cross-sectional study.
A total of 366 consecutive adult patients in whom clinicians performed urinalysis to diagnose or exclude UTI.
An urban emergency department and walk-in clinic.
After the patient encounter, but before dipstick test or culture was done, clinicians recorded the signs and symptoms that were the basis for suspecting UTI and for performing a urinalysis and an estimate of the probability of UTI based on the clinical evaluation. For all patients who received urinalysis, dipstick tests and culture were done in the clinical microbiology laboratory by medical technologists blinded to clinical evaluation. Sensitivity for the dipstick was calculated using a positive result in either leukocyte esterase or bacterial nitrite, or both, as the criterion for a positive dipstick, and greater than 10(5) CFU/mL for a positive culture.
In the 107 patients with a high (greater than 50%) prior probability of UTI, who had many characteristic UTI symptoms, the sensitivity of the test was excellent (0.92; 95% CI, 0.82 to 0.98). In the 259 patients with a low (less than or equal to 50%) prior probability of UTI, the sensitivity of the test was poor (0.56; CI, 0.03 to 0.79).
The leukocyte esterase and bacterial nitrite dipstick test for UTI is susceptible to spectrum bias, which may be responsible for differences in the test's sensitivity reported in previous studies. As a more general principle, diagnostic tests may have different sensitivities or specificities in different parts of the clinical spectrum of the disease they purport to identify or exclude, but studies evaluating such tests rarely report sensitivity and specificity in subgroups defined by clinical symptoms. When diagnostic tests are evaluated, information about symptoms in the patients recruited for study should be included, and analyses should be done within appropriate clinical subgroups so that clinicians may decide if reported sensitivities and specificities are applicable to their patients.
确定用于诊断尿路感染（UTI）的白细胞酯酶和细菌亚硝酸盐快速试纸检测是否易受谱偏倚影响（即当诊断检测对于该检测所针对疾病的不同临床表现患者具有不同的敏感性或特异性时）。
横断面研究。
共有366例成年患者，临床医生对其进行尿液分析以诊断或排除UTI。
城市急诊科和无需预约的诊所。
在患者就诊后，但在进行试纸检测或培养之前，临床医生记录了怀疑UTI并进行尿液分析的体征和症状，以及基于临床评估对UTI可能性的估计。对于所有接受尿液分析的患者，医学技术人员在临床微生物实验室进行试纸检测和培养，检测人员对临床评估情况不知情。以白细胞酯酶或细菌亚硝酸盐或两者呈阳性结果作为试纸检测阳性标准，培养结果大于10(5) CFU/mL为阳性，计算试纸检测的敏感性。
在107例先前UTI可能性高（大于50%）且有许多典型UTI症状的患者中，该检测的敏感性极佳（0.92；95%CI，0.82至0.98）。在259例先前UTI可能性低（小于或等于50%）的患者中，该检测的敏感性较差（0.56；CI，0.03至0.79）。
用于UTI的白细胞酯酶和细菌亚硝酸盐试纸检测易受谱偏倚影响，这可能是先前研究中该检测敏感性存在差异的原因。作为一个更普遍的原则，诊断检测对于其旨在识别或排除的疾病临床谱的不同部分可能具有不同的敏感性或特异性，但评估此类检测的研究很少报告按临床症状定义的亚组中的敏感性和特异性。在评估诊断检测时，应纳入所招募研究患者的症状信息，并应在适当的临床亚组内进行分析，以便临床医生能够确定所报告的敏感性和特异性是否适用于他们的患者。
