Clicky

TabletWise.com
Pharmacy Website
Clinic Website
 
 

Absolute Lymphocyte Count (ALC)

Calculators  Hematology
The Absolute Lymphocyte Count (ALC) is used to predict the CD4 count by assessing the number of lymphocytes.
Lymphocytes
%
White Blood Cell Count
Per 1000. Enter as 8.4, not 8400
×
Result:

Background

Measured Factor
ALC
Measured Factor Disease
  • Opportunistic infections
  • HIV
  • AIDS
Measured Factor Detail
The ALC can be used to predict a CD4 count. Low CD4 count identifies patients with increased risk of opportunistic infection, such as those with progression of HIV-1 infection. Moreover, the ALC is useful when measurement of CD4 count is expensive and often unavailable in third world countries.
Speciality
Multi-Speciality
Body System
Hematology
Formula
ALC = white blood cell count x lymphocyte percentage
Measured Factor Low Impact
  • An ALC <1,000 cells/mm3 is predictive of a CD4 count <200 cells/mm3
  • A CD4 count <200 cells/mm3 in a HIV-positive patient means that he/she is diagnosed to have AIDS, according to the United States Centers for Disease Control
  • An ALC of 1000 - 2000 cells/mm3 is not predictive of CD4 count
Measured Factor High Impact
  • An ALC ≥2,000 cells/mm3 is predictive of a CD4 count ≥200 cells/mm3
Process
White blood cell count (per 1000) is multiplied by lymphocytes percentage to give ALC. ALC and CD4 count were proportionally correlated.
Preparation
  • A blood test is used to determine white blood cell count and lymphocyte percentage.

Result Interpretation

Ranges Ranges
  • Normal: ≥2,000 cells/mm3
  • Normal Adult Male: ≥2,000 cells/mm3
  • Normal Adult Female: ≥2,000 cells/mm3
  • Normal Geriatric Male: ≥2,000 cells/mm3
  • Normal Geriatric Female: ≥2,000 cells/mm3
Result Low Conditions
  • Opportunistic infections
  • HIV
  • AIDS
Test Limitations
The ALC test was found to have low specificity in some cases. A retrospective multicenter 5-year study of  686 HIV+ patients with Pneumocystis jiroveci pneumonia by Napoli AM et al. showed an ALC < 1700 cells/mm3 had a high sensitivity (84%) and low specificity (55%) to predict a CD4 count < 200 cells/mm3. This study concluded that due to low specificity, the ALC method is not likely to be reliable as the only method to identify HIV+ patients with Pneumocystis jiroveci pneumonia.  

Another study by Shapiro NI et al. showed that an ALC less than 2,000 cells/mm3 predicted CD4 counts less than 200 cells/mm3 with a specificity of .41 (.37 to .45). Eventhough the ALC test is useful in identifying patients with increased risk of opportunistic infection, its specificity may be low.
References: 2, 3

Studies

Study Validation 1
A study of 2777 HIV-1-positive patients showed that a total lymphocyte count ≤ 2x10^9/L had high sensitivity (90.3%) to predict patients with a CD4 count < 200 cells/mm3, but low specificity (53.7%). When the total lymphocyte count cutoff value was lowered, specificity increased but sensitivity decreased. CD4  count and total lymphocyte count were correlated; however, this correlation was weakened when patients were stratified into three groups according to their CD4 count. Therefore, total lymphocyte count is not a good predictor of the CD4+ count in HIV-1 positive patients. This study looked at total lymphocyte count and not ALC, which might be acceptable since lymphocyte count, and not other white cell counts, is affected by HIV.
References: 4
Study Validation 2
A retrospective multicenter 5-year study of  686 HIV+ patients with Pneumocystis jiroveci pneumonia showed a moderate correlation between ALC and CD4 count  (r= 0.60, 95% CI 0.55-65, p < 0.01). An ALC < 1700 cells/mm3 had a high sensitivity (84%) and low specificity (55%) to predict a CD4 count < 200 cells/mm3. Due to low specificity, the ALC method is not likely to be reliable as the only method to identify HIV+ patients with Pneumocystis jiroveci pneumonia.
References: 5

Authors

Nathan Shapiro, MD, is a physician and professor in the Department of Emergency Medicine at Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States. He is also a director at the Center for Vascular Biology Research. Dr. Shapiro's research focuses on endothelial cell dysfunction in sepsis
https://connects.catalyst.harvard.edu/Profiles/display/Person/17353

References

  1. Shapiro NI, Karras DJ, Leech SH, Heilpern KL. Absolute lymphocyte count as a predictor of CD4 count. Ann Emerg Med. 1998 Sep;32(3 Pt 1):323-8.
  2. Napoli AM, Maughan B, Murray R, Maloy K, Milzman D. Use of the relationship between absolute lymphocyte count and CD4 count to improve earlier consideration of pneumocystis pneumonia in HIV-positive emergency department patients with pneumonia. J Emerg Med. 2013 Jan;44(1):28-35
  3. Shapiro NI, Karras DJ, Leech SH, Heilpern KL. Absolute lymphocyte count as a predictor of CD4 count. Ann Emerg Med. 1998 Sep;32(3 Pt 1):323-8.
  4. van der Ryst E, Kotze M, Joubert G, Steyn M, Pieters H, van der Westhuizen M, et al. Correlation among total lymphocyte count, absolute CD4+ count, and CD4+ percentage in a group of HIV-1-infected South African patients. J Acquir Immune Defic Syndr Hum Retrovirol. 1998 Nov 1;19(3):238-44.
  5. Napoli AM, Maughan B, Murray R, Maloy K, Milzman D. Use of the relationship between absolute lymphocyte count and CD4 count to improve earlier consideration of pneumocystis pneumonia in HIV-positive emergency department patients with pneumonia. J Emerg Med. 2013 Jan;44(1):28-35.