Is a negative gram stain in suspected septic arthritis sufficient to rule out septic arthritis
Date First Published:
June 6, 2008
Last Updated:
June 13, 2012
Report by:
Anna O Malley, Medical Student (University of Manchester )
Search checked by:
Helene Svinos, University of Manchester
Three-Part Question:
In [adults with suspected arthritis] is [a negative Gram stain of the joint aspirate ]sufficient [to rule out septic arthritis]
Clinical Scenario:
A 30 year old Nurse presents to the ED with two day history of a hot, swollen joint. She reports no prior knee swelling and no recent trauma or knee surgery, illegal drug use, rash, uvetis or risky sexual behavior. On examination, she is afebrile and has a left knee effusion. Her WBC, ESR and CRP are all raised. The joint aspirate reports a negative gram stain. You wonder if negative gram stain is enough to rule out septic arthritis?
Search Strategy:
Multifile search using OVID – Medline (1950-2008), Embase (1980-2008), CINHAL (1982-2008), Cochrane ({[exp.Infectious Arthritis OR hot joint.mp OR septic arthritis.mp OR septic joint.mp] AND [exp. Gram stain OR gram stain$.mp] AND [exp Synovial Fluid OR aspirate$.mp OR synovialfluid$.mp]}) Limited to Humans, English Language and Adults
Outcome:
The following number of articles were identified from each of the databases: Medline 20 citations, Embase 22 citations, CINAL 0 citations, Cochrane 1 citations. Duplicates and irrelevant titles removed from 43 articles leaving a total of 8 relevant articles.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| How sensitive is the synovial fluid white blood cell count in diagnosing septic arthritis? Daniel C, et al. 2007 USA | 49 culture positive synovial fluid aspirates in an ED in an urban tertiary care center | Case Series (Level 3) |
Gram stain | Negative in 27/49 (55%;95%CI, 37-74%) | Imperfect Gold standard* |
| Septic arthritis in a tertiary care hospital Nausha A, et al 2006 Pakistan | 116 patients from a tertiary care hospital identified by the ICD 711 as having SA | Retrospective Cohort (Level 3) |
Gram Stain | 78/116(67.2%) had a gram stain done 26/78 (33.3%) stained positive for a specific organism and 52/78 (66.7%) inconclusive | Small sample. Narrow definition of SA. |
| Gram staining in the diagnosis of septic arthritis Faraj A, et al. 2002 UK | 22 patients of who had arthroscopic lavage following a provisional diagnosis of SA who later were all found to have culture proven SA | Case Series (Level 3) |
Gram Stain | Sensitivity 45% Specificity 100% | Case Series. Small sample. No confidence intervals |
| Does the Adult Patient have Septic Arthritis? Margaretten et al. 2008 USA | Fourteen studies involving 6242 patients, of whom 653 diagnosed with SA and met all respective inclusion criteria. | Systematic Review (Level 1) | Gram Stain | Seven studies identified that reported sensitivities of 29-50%[1-5] | No confidence intervals. Imperfect gold standard* |
| Synovial leukocytosis in infectious arthritis. McCutchan HJ, et al. 1989 USA | 41 patients diagnosed with SA on a positive cultures | Case Series(Level 3) | Gram Stain | Positive | Case Series. Small Sample |
Author Commentary:
There is no evidence to suggest that a gram stain is sensitive enough to rule out septic arthritis such that a negative gram stain should not be taken as evidence to rule out SA.[1-8] This is supported by studies that have noted the absence of gram stain with a positive culture.[Mc Cutchan, Daniel] Most of the studies of the value of gram stain have been case series, therefore specificity is often not calculated. In the one retrospective study that looked at patients undergoing arthroscopic lavage following a provisional diagnosis of SA, specificity was calculated as 100%. [Faraj] A positive gram stain can therefore rule in (Spin) SA.
Bottom Line:
A negative gram stain is not sufficiently sensitive to rule out septic arthritis. A positive gram stain is sufficient to rule in SA.
*Imperfect Gold Standard –gram stain (sensitivity 29-50%) and culture (sensitive-82%)[Margaretten].
*Imperfect Gold Standard –gram stain (sensitivity 29-50%) and culture (sensitive-82%)[Margaretten].
References:
- Daniel C, et al. . How sensitive is the synovial fluid white blood cell count in diagnosing septic arthritis?
- Nausha A, et al. Septic arthritis in a tertiary care hospital
- Faraj A, et al. . Gram staining in the diagnosis of septic arthritis
- Margaretten et al. . Does the Adult Patient have Septic Arthritis?
- McCutchan HJ, et al. . Synovial leukocytosis in infectious arthritis.
- Soderquist B.. Bacterial or Crystal –associated Arthritis? Discriminating Ability of Serum Inflammatory Markers.
- Krey PR. . Synovial fluid leukocytosis :a study of extremes.
- Korekangas P. . Synovial fluid in bacterial arthritis vs. reactive arthritis and rheumatoid arthritis in the adult knee.